Recipe

Ingredients

Rainbow Cake

  • 2 boxes vanilla cake mix (Betty Crocker Super Moist Delights French Vanilla)
  • 2 cups water
  • 1 cup vegetable oil
  • 6 eggs
  • 6 drops blue Americolor Softgel Paste food coloring
  • 6 drops red Americolor Softgel Paste food coloring
  • 6 drops green Americolor Softgel Paste food coloring
  • 6 drops yellow Americolor Softgel Paste food coloring
  • 6 drops orange Americolor Softgel Paste food coloring
  • 6 drops purple Americolor Softgel Paste food coloring

Rainbow Cake Buttercream Crumb Coat

  • 2 cups unsalted butter, softened
  • 8 cups powdered sugar
  • 2 teaspoons pure vanilla extract
  • 1 teaspoon salt
  • 3 tablespoons milk

Rainbow Cake Final Buttercream Coat

  • 1 cup unsalted butter, softened
  • 4 cups powdered sugar
  • 1 teaspoon pure vanilla extract
  • 1/2 teaspoon salt
  • 2 tablespoons milk

Directions

Rainbow Cake

  1. Preheat your oven to 350 degrees. Grease 3 8-inch round cake pans with butter, dust them with flour, and set them aside.

  2. In a stand mixer fitted with a paddle attachment, beat the cake mix, water, oil, and eggs on medium speed for 2 minutes, scraping the bowl periodically with a silicone spatula. Mix thoroughly.

  3. Divide the cake batter evenly into 6 small bowls.

  4. Using the food coloring, begin to tint the batter in the bowls. Tint the batter in the first bowl blue. Tint the batter in the next bowl red. Tint the batter in the third, fourth, fifth, and sixth bowls green, yellow, orange, and purple, respectively.

  5. Pour the purple, blue, and green cake batters into their individually prepared cake pans. Lightly tap the pans on the counter before placing them into the oven; this will dislodge any large air bubbles.

  6. Bake the cakes for 15-18 minutes or until a toothpick inserted in the center comes out clean. Meanwhile, refrigerate the 3 remaining cake batters until you are ready to use them.

  7. Let the purple, blue, and green cakes cool in their pans for at least 10 minutes. Run a butter knife around the edges of the cakes to loosen them from the sides of the pans. Then invert the cakes onto cooling racks and allow them to cool completely.

  8. Wash the cake pans. Bake and cool the remaining cake batters in the same way you baked and cooled the others.

Rainbow Cake Buttercream Crumb Coat

  1. While the cakes cool, prepare the frosting for the crumb coat. Cream the butter on medium speed in the bowl of a stand mixer fitted with a whisk attachment.

  2. Gradually add the powdered sugar and beat on low speed. Mix until the sugar and butter are combined.

  3. Add the vanilla and the salt to the frosting mixture. Continue to mix on medium-high speed until the frosting becomes smooth.

  4. Add the milk to adjust the thickness of the frosting. If you desire a thinner consistency, add more milk, 1 tablespoon at a time. If the frosting becomes too thin, simply add more powdered sugar.

  5. When your cakes are completely cool, use a serrated knife to level them. This will allow you to stack them more easily.

  6. Start to assemble your cake on a serving plate, cake stand, or cake turntable. Place a dab of buttercream in the center of the serving plate and place the purple cake layer on top. The dab of buttercream will help secure the cake to the serving plate.

  7. Add the buttercream to the center of the purple cake layer using a long offset spatula. Spread the buttercream until you come within 1/4 of an inch of the edge of the cake layer.

  8. Repeat Step 7 with the blue, green, yellow, orange, and red cake layers.

  9. Spread a thin coat of buttercream on the top of the cake as well as a thin layer on the sides -- just enough to lock in the crumbs of the cake.

  10. Carefully place the cake in the refrigerator to chill for at least 30 minutes. This will allow the buttercream to firm up for the final coat of frosting.

Rainbow Cake Final Buttercream Coat

  1. While the cake chills in the refrigerator, prepare the frosting for the final coat of buttercream. Cream the butter on medium speed in the bowl of a stand mixer fitted with a whisk attachment.

  2. Gradually add the powdered sugar and beat on low speed. Mix until the sugar and butter are combined.

  3. Add the vanilla and the salt to the frosting mixture. Continue to mix on medium-high speed until the frosting becomes smooth.

  4. Add the milk to adjust the thickness of the frosting. If you desire a thinner consistency, add more milk, 1 tablespoon at a time. If the frosting becomes too thin, simply add more powdered sugar.

  5. Remove the cake from the refrigerator after 30 minutes have passed.

  6. Using a long offset spatula, top the center of your cake with buttercream. Carefully spread the frosting evenly just past the edges of the cake. Use the overhang of buttercream to coat the sides of the cake.

  7. To achieve a smooth finish, use a bench scraper to smooth the sides of the cake. Hold the bench scraper parallel to the cake and slowly rotate the serving plate or turntable.

  8. Use the bench scraper to smooth the top of the cake as well. Apply a small offset spatula to smaller areas that need to be touched up.

  9. Enjoy!

Supplies

Rainbow Cake

  • 3 8-inch round cake pans
  • stand mixer with both paddle and whisk attachments
  • silicone spatula
  • 6 small bowls
  • 3 cooling racks
  • serrated knife
  • serving plate, cake stand, or cake turntable
  • long offset spatula
  • bench scraper
  • small offset spatula

Recipe Notes

If you only have 2 8-inch cake pans, bake the cakes in 3 batches instead.

To achieve vibrant colors, be sure to use gel food coloring. Using liquid food coloring will result in a pastel look.

Check out these essential baking tools every home baker needs.

Anyone can prepare this cheerful, picture-perfect rainbow cake! You'll need a couple of boxes of vanilla cake mix and six different kinds of food coloring, and you'll need to whip up our deliciously sweet buttercream frosting. Baking this cake will take a little time, but if you follow our simple step-by-step recipe, you'll have one impressive dessert to share with your family and friends.

Adding A Crumb Coat

rainbow cake layers
Brittany Baxter

Adding a crumb coat is an essential part of the cake-decorating process. Although a crumb coat won't change the flavor of your cake, it will seal in any loose crumbs on the cake and create a smooth finish. If you're going for that wow effect, don't skip the crumb coat.

This rainbow cake is visually stunning and is sure to impress anyone who catches a glimpse or gets a taste. Try this easy-to-follow recipe the next time you want to create a showstopping cake.

Subscribe to the Oola Newsletter

Oven-Baked Potato Skins Recipe Life in Flavor Brittany Baxter Read More
Florentine Cookies Life in Flavor Brittany Baxter Read More
Gluten Free Apple Galette Life in Flavor Brittany Baxter Read More
Cookie Settings