Double Rainbow Happiness Cake
Work: 1 hour 30 minutes
Total: 2 hours 40 minutes
3 boxes white cake mix, batter prepared
Gel paste food coloring
8 large egg whites
2 cups sugar
6 sticks unsalted butter, softened
1 1/2 teaspoons vanilla extract
1/3 cup apricot jam
1/4 cup white sprinkles
- Heat oven to 350 degrees F. Grease two 9-by-5-inch straight-sided loaf pans and line bottoms with parchment. Pour 1 rounded cup cake batter into each of 7 bowls and color with food coloring. We made fuchsia, light pink, peach, purple, yellow, green, and turquoise.
- Pour two batters into prepared loaf pans. Bake for 15 minutes, until cooked through. Allow cakes to cool slightly, remove cake, wipe pans clean, and repeat with remaining batter.
- For buttercream frosting, whisk egg whites and sugar in a heatproof bowl over a pan of simmering water until sugar is dissolved, about 5 minutes. Remove from heat; beat on high speed until stiff peaks form, 6 to 10 minutes. Reduce speed and add butter a few tablespoons at a time until incorporated. Add vanilla and stir until smooth.
- Trim domed tops from cakes and place one cake on a serving platter. Combine apricot jam with 3 cups buttercream and spread about 1/2 cup onto each layer. Smooth a thin layer (a "crumb" coating) of the remaining buttercream all over the cake and chill for 20 minutes. Frost again with a final coat of buttercream and top with sprinkles. Serves 14.