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Easy 6 Layer Rainbow Cake Recipe with Easy Buttercream Frosting

Learn how to make this easy rainbow cake recipe using boxed cake mix. This cool cake idea is perfect for birthdays! You can swirl the buttercream rainbow cake for a tie dye cake or make a 6 layer rainbow cake. No matter how you bake it, this big rainbow cake is the perfect dessert for every celebration!

Easy Rainbow Buttercream Cake

This homemade dessert recipe for a 6 Layer Rainbow Cake Recipe is easier than it looks thanks to boxed cake mix. The beautiful and vibrant colored layers really make a statement especially when it’s topped off with a delicious homemade buttercream frosting!

Turning 30 is definitely a milestone birthday. Maybe not physically but definitely mentally.

Buttercream rainbow cake layered on plate.

So to celebrate turning 30, I did something a little bigger and more memorable for my birthday dessert. This was definitely more time consuming and elaborate production than the birthday cookie cake I made for my husband.

Or the Cars birthday cake I made for Brady. It was big, beautiful, and absolutely delicious!

White buttercream frosted rainbow layer cake for 30th birthday party with candles.

Where does anyone go these days when searching for inspiration? Pinterest, of course!

I have zero experience working with fondant and since I didn’t want my cake to be an unappetizing mess, I looked for something memorable that didn’t include fondant.

frosted layer cake

One possibility that kept popping up was for a 6 layer rainbow cake recipe, hidden beneath some unassuming buttercream frosting. It looked pretty straightforward but made a big statement, so I went with it.

A picture from Martha of her multi layer cake was all I needed to start work. I knew I wouldn’t need to use or modify her recipe though.

But how do you make a 6 layer rainbow cake recipe easy? Don’t spend time mixing cake flour with other dry ingredients just to have a completely homemade cake.

I didn’t want this to take a long time. So, I had on shame in taking shortcuts when I’m cooking. Using boxed vanilla cake mix to make my life easier seemed like a no-brainer.

And with two small kids running around, it fits my needs perfectly. Fair warning, you will be using lots of bowls.

If you’re looking for some birthday cake inspiration or something for your St. Patrick’s Day party that will really wow all of your family and friends, then I’d definitely urge you to give this easy 6 layer rainbow cake recipe a try.

Layered Rainbow Cake Ingredients

  • White cake mix, you could also make your own using a base of all purpose flour
  • Eggs (egg whites and egg yolks)
  • Canola oil
  • Water
  • Wilton gel food coloring

Homemade Frosting Ingredients

  • Powdered sugar
  • Unsalted Butter
  • Milk
  • Clear vanilla extract

How to make layers of frosting

To make this colorful cake as easy as possible, you need to start the night before. Use a piece of wax paper and a pencil to trace the outline of the bottom of your cake pan.  

You can use disposable round cake pans for tracing. The disposable cake tins I bought had a curved bottom, so I used my own 9″ cake pan which had a uniform edge.

From your template, you need to make 14 circles made of wax paper or parchment paper for this project. Cut out the circular wax paper pieces.

Use a stand or hand mixer and combine all buttercream frosting ingredients together until light and fluffy.  If your frosting ends up too thick, continue adding milk 1 tablespoon at a time until the mixture is the consistency you’re looking for.

Spread a thin layer of buttercream frosting on a wax paper cake pan template.  Cover with a new circle and repeat.

Stack your layers of buttercream frosting, until you have one wax circle left to place on top.  You will have one extra layer of buttercream frosting in case any of your layers fall apart during assembly.

Carefully place your dividing layers of buttercream in the freezer until ready to assemble your cake the following day. Refrigerate the remainder of buttercream frosting until ready to frost cake.

Set aside remaining wax circles until the following day when you’ll coat with cooking spray and use these to line the bottom of your disposable baking pans.  Lightly spray additional cooking spray to sides of cake pans.

When the butter cream frosting is done, you’ll begin making the layers between each color. You’ll also freeze the cream butter frosting so it’s easier to spread the next day.

If you don’t have time to freeze the frosting, that’s ok too. This frosting will also work at room temperature.

Frozen buttercream frosting layers.

It’s totally ok if the buttercream frosting layer breaks. No one will ever know!

How to make a rainbow layer cake

The next day, preheat your oven according to cake mix box directions – usually 350 degrees.

Place cake mix, eggs, oil, and water together and blend with a stand mixer or electric mixer with a large bowl on medium speed. Continue to mix until incorporated (about 2 minutes). Evenly divide batter into separate bowls.

Big rainbow layer cake with individual colors baked.

Once it’s divided, tint batter by adding a few drops of food coloring (gel food colors will give the colorful layers) at a time to each bowl until the desired color for each layer is reached. I went with red, orange, yellow, green, blue, and purple.

You could also change up the colors of batter and get a true ROYGBIV cake. Getting a true indigo layer will be a breeze with these gel food colors. Using this same recipe, it can be made into a 7 layer rainbow cake by using a little less cake batter for each of the layers of the cake. 

Then, transfer the colored batter to disposable cake pans. Make sure to scrape the sides of the pan to get all of the colored batter out.

Place prepared pans into the preheated oven and cook for approximately 8-12 minutes.  Make sure to keep an eye on your cakes during this stage as cooking times will vary.

These cakes are very thin so won’t cook like a traditional cake will. A toothpick inserted into the cake should come out clean.

Cool cake idea different rainbow colors of cake.

Once the cakes are baked, allow them to cool completely in the pans for 10 minutes. Then invert on baking sheets or a wire rack to finish cooling.

For best results, once the cakes are cooled, use a serrated knife to make flat layers on top of each cake. This will allow them to stack more easily.

Assembling a Layer Cake

Before assembling the rainbow layers of your cake, prep a foil-lined baking sheet or cake stand. This cake will be assembled in the reverse order than you might think.

The first layer of cake will actually be the bottom layer. So you’ll start with the purple cake layer.

Tie dye rainbow colored layer cake.

Begin alternating a layer of cake with a layer of buttercream frosting in order of the rainbow. The top layer of your cake will be the red layers.

A 6 layer cake can be pretty heavy. To stabilize it, place three straws in the cake.  Cut the tops of the straws so they’re flush with the cake.

How to make a rainbow layer cake. Shows rainbow layers with straws as inner supports of cake.

You can skip this step if you want, but I can’t guarantee your cake won’t collapse under all the weight. This is a tall cake and can be pretty heavy as well.

How to Frost a Layer Cake

Icing a cake this size can be really tricky.  Placing it on a cake plate, cake stand, or board will make your life easier.

I used a rubber spatula to plop some frosting on top of the cake. Then I used a metal offset spatula to smooth it all over the sides of the cake creating a thin layer to seal in the crumbs.

Big rainbow layer cake with crumb cake cake frosting layer.

The crumb layer step is a little bit tricky but is necessary as it will help seal all of the crumbs in. It also helps ensure you’ll have a smooth frosting layer.

After the crumb coat, apply a thick layer of buttercream frosting. This will be your final coat.

I used the edge of a metal spatula to smooth out this cake. You could also use a bench scraper if you’re looking for perfection.

Homemade buttercream frosted rainbow cake idea.

The rainbow cake frosting on this cake is really unassuming. But it’s sure to surprise those around when the vibrant colors of the rainbow are exposed beneath.

After your party guests have seen the inside of the finished cake, there will sure to be lots of questions? I bet number one will be, who gets the first slice?!

rainbow cake

To add a little more color to the outside, you can decorate it with sprinkles, candies, use a piping bag to add detail or even other colors of icing. You could also this cake topper to transform this into a rainbow cake with a unicorn!

Frequently Asked Questions (FAQ)

I only have 8-inch cake pans, will this recipe still work?

Yes, this will still be a perfect rainbow using the 8 inch pans. Just slightly smaller.

Do you have to use wax paper for your outlines?

No, you don’t have to use wax paper for the thin layer of frosting. You could also use parchment paper. 

What other frostings could I use to cover my homemade rainbow cake?

You could also use cream cheese frosting or swiss meringue buttercream and still have a delicious rainbow layer cake. 

Have you ever tried your hand at a 6 layer rainbow cake recipe? For more easy cake recipes and rainbow cake ideas, check out the other fun creations below!

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Pin this rainbow buttercream cake for later! 

Buttercream frosted 6 layer rainbow cake for birthdays.
Big rainbow cake with slice cut.

More buttercream frosting recipes:

Check out these rainbow recipes:
Looking for an eye catching dessert recipe for St Patrick's Day? Check out these Easy Chocolate Cupcakes Recipe from Scratch + Rainbow Buttercream Frosting

6 Layer Rainbow Cake with Easy Buttercream Frosting Recipe

4.34 from 12 votes
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6 Layer Rainbow Cake Recipe with Easy Buttercream Frosting

This homemade dessert recipe for a 6 Layer Rainbow Cake Recipe is easier than it looks thanks to boxed cake mix. Nonetheless, the beautiful and vibrant colored layers really make a statement especially when it’s topped off with a delicious homemade buttercream frosting!

Course Dessert
Cuisine American
Keyword buttercream, cake, frosting, rainbow
Servings 20
Calories 456 kcal

Ingredients

For Cake:

Ingredients for Buttercream Frosting

Instructions

  1. The night before preparing the cakes and assembling, using a piece of wax paper and a pencil trace the outline of the bottom of your cake pan.  You can use the disposable cake pans for tracing but the disposables I bought had a curved bottom so I used my own 9″ cake pan which had a uniform edge.  From your template, you’re going to make 14 circles made of wax paper for this project.
  2. Cut out the circular wax paper pieces.
  3. Mix all buttercream frosting ingredients together until desired consistency.  If your frosting ends up too thick, continue adding milk 1 tablespoon at a time until the mixture is what you’re looking for.
  4. Spread a thin layer of buttercream frosting on a wax paper cake pan template.  Cover with a new circle and repeat, stacking your layers of buttercream frosting, until you have one wax circle left to place on top.  You will have one extra layer of buttercream frosting in case any of your layers fall apart during assembly.
  5. Carefully place your dividing layers of buttercream in the freezer until ready to assemble your cake the following day.
  6. Refrigerate remainder of buttercream frosting until ready to frost cake.
  7. Set aside remaining wax circles until the following day when you’ll coat with cooking spray and use these to line the bottom of your disposable baking pans.  Lightly spray additional cooking spray to sides of cake pans.
  8. The next day, preheat your oven according to cake mix box directions – usually 350 degrees.
  9. Mix cake mix, eggs, oil, and water together until blended (about 2 minutes).
  10. Evenly divide cake batter in mixing bowls.

  11. Add gel food coloring to each individual bowl, adding a small amount at a time until you achieve your desired colors.

  12. Pour batter into baking pans and place all pans in oven to cook for approximately 8-12 minutes.  Make sure to keep an eye on your cakes during this stage as cooking times will vary and these cakes are very thin.

  13. Once cakes are done, allow to cool in pan for 10 minutes before inverting pans on baking racks to finish cooling.

  14. When the cakes are cooled, if needed using a serrated knife cut tops to make flat edges for the layers.

  15. On a cake stand or foil covered surface, place your bottom layer of cake followed by a frozen layer of buttercream frosting.  Continue alternating cake and frosting until all layers are assembled.  Since this cake is so heavy, I cut three straws to the height of the cake and stuck them into the cake to provide stability.

  16. Icing a cake this size can be really tricky.  I used a plastic spatula to plop some frosting on top of the cake, then I used a metal offset spatula to smooth it all over creating a thin layer to seal in the crumbs.  Then repeat using more icing and spread an even layer of buttercream frosting on your cake.  You can use the edge of your metal spatula to smooth things out.  If you’re looking for an even smoother, more finished look I’ve heard a bench scraper would really make a difference and get the job done perfectly.

Recipe Video

Nutrition Facts
6 Layer Rainbow Cake Recipe with Easy Buttercream Frosting
Amount Per Serving
Calories 456 Calories from Fat 171
% Daily Value*
Fat 19g29%
Saturated Fat 7g35%
Cholesterol 73mg24%
Sodium 381mg16%
Potassium 56mg2%
Carbohydrates 66g22%
Sugar 45g50%
Protein 3g6%
Vitamin A 360IU7%
Calcium 128mg13%
Iron 1.3mg7%
* Percent Daily Values are based on a 2000 calorie diet.
Recipe Rating




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