Rainbow Marble Cake with Homemade Buttercream Frosting 🎂
A vibrant cake with colorful swirls inside and out, perfect for any celebration.
Ingredients:
Rainbow Marble Cake:
3 cups all-purpose flour
3 cups granulated sugar
2 1/2 tsp baking powder
1 tsp salt
1 cup unsalted butter, room temperature (2 sticks)
2 tsp vanilla extract
1 cup egg whites (about 7 egg whites)
1 1/2 cups buttermilk, room temperature
1/8 cup vegetable oil
Gel food coloring (purple, blue, green, yellow, orange, red)
Vanilla Buttercream Frosting:
3 cups unsalted butter, room temperature
11 cups powdered sugar
1 tsp salt
1/3 cup heavy cream (or whipping cream)
1 1/2 Tbsp vanilla extract
Gel food coloring (purple, blue, green, yellow, orange, red)
Directions:
Vanilla Cake Layers:
Preheat oven to 350°F. Line three 8-inch round pans with parchment rounds, grease.
Mix dry ingredients (flour, baking powder, sugar, salt) in a stand mixer with a paddle until combined.
Slowly add room-temperature butter, mix until crumbly.
Add egg whites, mix on low until incorporated.
Mix in buttermilk in two installments on low speed.
Add vanilla and oil, mix on low until incorporated. Scrape bowl, beat on medium for 30 seconds.
Divide batter into six bowls, color each with gel food coloring.
Spoon blue and purple batter into one pan, swirl with a knife. Repeat with remaining colors and pans.
Bake for 34-37 minutes, cool for 10 minutes, then freeze layers for 45 minutes.
Vanilla Buttercream Frosting:
Beat butter on medium for 30 seconds. Slowly add powdered sugar, alternating with cream.
Add vanilla and salt, beat on low until incorporated. Adjust consistency with cream or powdered sugar as needed.
Color remaining buttercream after cake assembly.
Assemble the Cake:
Stack and frost cake layers on a greaseproof cake board with a dab of frosting.
Add an even layer of buttercream between layers.
Apply a thin crumb coat, chill until firm.
Add a second, thicker layer of frosting, smooth with a bench scraper.
Divide remaining buttercream, color with gel food coloring.
Pipe rainbow frosting around the sides with French piping tips.
