Rainbow Cake Recipe

Rainbow layer cake recipe made with 4 cake layers

4.85 from 91 ratings

Wow your guests with this stunning rainbow layer cake! Learn the secrets to vibrant, moist layers and creamy frosting in this foolproof recipe.

Prep Time15

Cook Time35

Additional Time1

Total Time1 50

Course: Cakes

Cuisine: American

Servings: 24

Calories: 660kcal

Author: Chelsey White

Ingredients

Rainbow Cake Layers

3 cups all-purpose flour 390g
3 cups granulated sugar 600g
2 1/2 tsp baking powder 10g
1 tsp fine salt 6g
1 cup unsalted butter, room temperature 226g - 2 sticks
1 Tbsp vanilla extract or vanilla bean paste 12g
1 cup carton egg whites or 7 large egg whites, room temperature 240g
1 1/2 cups buttermilk, room temperature 345g
1/8 cup vegetable or canola oil 28g
Red, yellow, blue, and pink gel food coloring

Vanilla Buttercream Frosting

3 cups unsalted butter, room temperature 678g
11 cups powdered sugar 1375g
1 tsp fine salt 6g
1/3 cup heavy whipping cream, room temperature 75g
1 1/2 Tbsp vanilla extract or vanilla bean paste 18g
Red, orange, yellow, green, blue, purple, and pink gel food coloring

Instructions

Rainbow Cake Layers

Preheat the oven to 350°F. Line four, 7-inch round cake pans with parchment rounds and grease with a light spray of non-stick cooking spray.
Mix together all dry ingredients (3 cups flour, 2 1/2 tsp baking powder, 3 cups sugar, and 1 tsp salt) in a stand mixer with a paddle with a few gentle pulses.
Mix chunks of 1 cup room-temperature butter slowly into the dry mix on a low speed. Continue to mix until no large chunks of butter remain and the mixture becomes crumbly.
Pour in 1 cup of egg whites and mix on low until just incorporated. Mix in the 1 1/2 cups of buttermilk in two installments on a low speed.
Add in 1 Tbsp vanilla and 1/8 cup oil and mix at a low speed until fully incorporated. Scrape down the sides of the bowl with a spatula, then beat on low speed for about 15 seconds.
Divide the batter evenly between four bowls (about 450 grams of batter per bowl). Create red, yellow, blue, and pink batter using a couple of drops of gel food coloring. Mix by hand with a spatula until the batter is evenly colored.
Pour each color into one of the prepared cake pans.
Bake for 34-37 minutes or until a toothpick comes out clean. Allow the pans to cool for 10 minutes, then run an offset spatula around the perimeter of the pan to separate the cake from the pan.
Place cake layers into the freezer for 45 minutes to accelerate the cooling process. Once the layers are fully cooled, carefully flip the pans and remove the layers from the pans.
Use a serrated knife to level the tops of the layers, and then frost as desired.

Vanilla Buttercream Frosting

While the cake layers bake and cool, make the vanilla buttercream frosting.
Beat 3 cups of unsalted butter on a medium speed for 30 seconds with a paddle attachment, until smooth. Slowly add in the 11 cups powdered sugar, 1 cup at a time. Alternate with small splashes of 1/3 cup cream.
Once fully mixed, add in the 1 1/2 Tbsp vanilla and 1 tsp salt, and beat on low until the ingredients are fully incorporated and the desired consistency is reached.
If the frosting is too thick, add in additional cream (1 teaspoon at a time). If the frosting is too thin, add in more powdered sugar (quarter of a cup at a time).
To create the colorful buttercream used to fill the cake, place 1 cup of frosting into three separate bowls. Color them orange, green, and purple with a couple of drops of gel food coloring.
Leave the rest of the buttercream white until the cake has been assembled.

Assembling This Rainbow Cake

Stack and frost cake layers on a greaseproof cake board, using a dab of frosting to help stick the first cake layer to the board.
Start with the red cake layer on the bottom. Top with a thick layer of orange buttercream. Leave about 1/4 of a cup of frosting in the bowl to decorate the sides of the cake later.
Top with the yellow cake layer, then frost with the green buttercream, reserving a tiny bit of green buttercream.
Next, add the blue cake layer and top with some purple buttercream (leaving a bit for the decoration later).
Top the cake with the pink cake layer, placing it upside down to make it easier to frost (with the caramelization from the bottom of the pan facing upward).
Apply a thin coat of frosting around the cake, to fully cover the cake layers. Smooth using a bench scraper, then chill the cake in the fridge (10 minutes) or freezer (5 minutes) until the frosting is firm to the touch.
Add a second, thicker layer of frosting to the cake and smooth it using a bench scraper. Place the cake in the freezer to chill for 10-15 minutes or in the fridge for 30 minutes.
Place about 1 1/2 cups of white buttercream into a piping bag fitted with an Ateco 869 frosting tip (a very large French tip)
In four other small bowls, color about 1/2 cup of frosting to make red, yellow, blue, and pink buttercream.
Using a small offset spatula, spread dabs of each color of frosting around the chilled cake. Feel free to overlap and have fun with this step!
Top the cake with a border of white buttercream frosting, and then cut it and enjoy!

Video

Notes

Note: If you want to use whole eggs to make the cake batter instead of egg whites, you can use 4, room-temperature, large eggs.

How Many People Does This Cake Feed?

If you make this cake with 4, 7-inch cake layers or 3, 8-inch cake layers, it will feed about 24 people. For more information on cake sizes and servings, check out my cake portion guide.

Recipe Variations - Making This Cake in Different Sizes

One batch of this recipe makes about 10 cups of batter or about 1800 grams. If you plan to use four circular cake pans, add 450 grams of batter into each pan.

If you want to make a tiered cake or a different-sized cake with this recipe, check out my cake portion guide to see how many batches of batter you'll need.

This recipe can also be used to make a sheet cake! One batch will make a 1, 9 x13-inch cake layer that's about 1.5 inches tall once leveled.

Bake for 45-55 mins at 350 F / 175 C, or until a toothpick inserted in the center comes out with a few moist crumbs. Bake time can vary a lot based on the type of pan you use, if you use heating cores, and your oven. I recommend using heating cores if you have them; they help sheet cake layers bake more evenly and quickly.

For more details on how to convert this cake recipe and others into sheet cakes, check out my sheet cake guide.

Last but not least, you can also make cupcakes using this recipe. Fill the liners 3/4 full and bake them at 350 F / 175 C for 19-21 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Or, if you want to make just one batch of cupcakes, I highly recommend trying my vanilla cupcake recipe.

Tips for Making the Best Rainbow Layer Cake

Ingredients at room temperature mix together better! Set out any cold ingredients ahead of time.
Properly measure the flour (spoon it into the cup measure, then level). Or better yet, use a kitchen scale to measure your dry ingredients.
Use a scale to weigh your cake pans as you fill them. It will make your cake layers bake to the same height and bake more evenly.
Make sure the buttercream is the right consistency. This will help give the cake proper structure and make it easier to decorate.
Level the room temperature or thawed cake layers with a serrated knife to make them easier to stack.
Chill your cake layers in the freezer for about 20 minutes before assembling the cake. It makes it so much easier to stack and frost them!
If your cake layers turn out less than perfect, read my cake troubleshooting guide to see where things might've gone awry.

Making This Rainbow Layer Cake in Advance & Storage Tips

I highly recommend making the cake layers in advance and freezing them. It breaks the process up and makes it more approachable and enjoyable, and I promise they taste just as delicious!

You can also make the frosting ahead of time or save any leftover frosting! It can be stored in an airtight container in the fridge for up to a month or in the freezer for up to 3 months. Be sure to give it a good stir once it thaws to get the consistency nice and smooth again.

A frosted cake can last in the fridge for up to a week (as long as it doesn't have a perishable fruit filling) or in the freezer for up to a month. The buttercream locks in all the moisture, keeping the cake fresh and delicious!

If you cut into the cake and have leftovers, use any remaining frosting to cover the cut section to keep it moist and store it in the fridge for up to a week.

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