Rainbow Explosion Cake

Directions

Preheat a conventional oven to 350°F (180°C) or a convection oven to 325°F (165°C). Coat six 6-inch (15-cm) round cake pans with nonstick cooking spray.

Make the Batter

In the bowl of an electric mixer fitted with the flat beater, cream the butter on medium speed until light and fluffy, about 2 minutes. Stop the mixer and scrape down the sides of the bowl. With the mixer on medium speed, add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed. Reduce the mixer speed to low and add the cake mix in three additions, alternating with the milk and beginning and ending with the cake mix. Increase the mixer speed to medium-high and beat until the batter is smooth, about 1 minute.

Color the Batter

Divide the batter evenly among 6 bowls; there will be about 3/4 cup, or 7 oz./220 g, of batter in each bowl.

For the pink layer, add 1/8 tsp. of pink food coloring to one bowl of batter. Stir until the color is uniform and no streaks of white remain. Repeat to color the orange, yellow, green, blue and purple layers, using 1/8 tsp. for each color except for the purple, to which you should add 1/4 tsp. food coloring.

Bake the Layers

Pour each bowl of colored batter into a separate prepared cake pan. (If you don’t have 6 cake pans, you can bake the layers in batches.) The pans will be less than half full. In batches if necessary, bake the cakes, rotating the pans once during the baking time, until a toothpick inserted in the cakes comes out clean, 15 to 17 minutes. Transfer the cakes to wire racks and let cool in the pans for 10 minutes, then turn the cakes out on the wire racks to cool completely.

Make the Frosting

In the bowl of an electric mixer fitted with the flat beater, cream the butter and cream cheese on medium-high speed until smooth, about 1 minute. Reduce the mixer speed to low and slowly add the frosting mix. When all the frosting mix has been incorporated, increase the mixer speed to medium-high and beat until light and fluffy, about 2 minutes. You will have about 3 1/2 cups (28 oz./800 g) frosting.

Build the Cake

Using a 2-inch (5-cm) round cookie cutter or biscuit cutter, cut out a round from the center out of every cake except for the pink layer (which will be the top layer). Transfer about 1 cup (7 1/2 oz./235 g) of the frosting into a small bowl for building the cake, reserving the rest for the later steps.

If you have a cardboard cake round, spread a small ring of frosting in the center of the cake round. If you don’t have a cardboard round, place a ring of frosting in the center of your cake plate or cake stand. (This will keep the cake from sliding around as you assemble it.) Place the purple cake layer on top of the ring of frosting, centering it on the plate. Cover the purple layer with an even layer of the frosting, making sure not to cover the hole. Top with the blue layer, followed by another layer of frosting. Repeat with the remaining layers in this order: green, yellow and orange.

Pour the sprinkle explosion mix into hole, stopping when the hole is completely filled. (You may not use all of the sprinkle mix.) Finally, flip the pink cake layer upside down and place it on the top of the cake.

Apply the Crumb Coat

Transfer another 1 cup (7 1/2 oz./235 g) of the frosting to a small bowl for applying the crumb coat, reserving the rest for the final layer of frosting. Using an offset spatula or knife, apply a very thin, even layer of frosting to the sides and top of the cake. If your cake begins to tilt, carefully shift it back into place with your hands. Transfer the cake to the refrigerator for 20 minutes. (This will firm up the frosting and make it more stable for the final steps.)

Frost and Decorate the Cake

Using an offset spatula or knife, use the remaining frosting to completely cover the cake evenly. You want the surface of the cake to be as smooth as possible. Set the cake on a baking sheet lined with parchment paper. Next, place the rainbow polka dot sprinkles in a bowl. Making sure your hands are dry, pick up a small handful of the sprinkles. Working from the bottom of the cake up, gently press the sprinkles into the frosting. Continue around and on top of the cake until the entire cake is completely covered in sprinkles. As needed, return any sprinkles that have fallen onto the baking sheet back to the bowl so that you can use them again.

Serve

The cake is best served immediately but can be refrigerated for up to 3 days. Remove from the refrigerator about 1 hour before serving. Serves 15.

Recipe courtesy of Amirah Kassem, Flour Shop, NYC