How To Make the Ultimate Rainbow Surprise Cake
Serves15 to 18
Serves 15 to 18
For the cake layers:
- 4 1/2 cups
- 1 1/2 tablespoons
- 1 teaspoon
- 3 cups
- 3 sticks
(1 1/2 cups) unsalted butter, at room temperature
large egg yolks
- 2 cups
- 1 tablespoon
- 6 teaspoons
gel food coloring (6 colors, 1 teaspoon each, such as Cake Craft Coloring Gel Startup Kit)
For the American buttercream (makes about 6 cups):
- 1 pound
(2 cups) unsalted butter, at room temperature
- 7 to 8 cups
powdered sugar, divided
- 2 tablespoons
heavy cream or milk
- 2 teaspoons
For the filling and topping:
About 2 cups of a variety of edible sprinkles or candy-coated chocolate, such as:
Measuring cups and spoons
Stand mixer with a paddle attachment
Large and small mixing bowls
2 to 6 (9-inch) round cake pans
3-inch round cutter
Wire cooling rack
Long, sharp knife
Day 1: Bake the cake layers
Prepare your cake pans: Line 2 to 3 (9-inch) round cake pans with parchment paper rounds and coat with cooking spray. Arrange a rack in the middle of the oven and heat to 350°F.
Combine the dry ingredients: Place the cake flour, baking powder, and salt in a large bowl and whisk to combine.
Cream the butter and sugar: Place the butter and sugar in stand mixer fitted with a paddle attachment and beat on medium speed until the mixture is lightened in color and slightly increased in volume, about 5 minutes.
Add the egg yolks: Stop and scrape down the sides of the mixer with a rubber spatula. Return the mixer to low speed and add the egg yolks one at a time, allowing each to fully incorporate into the batter before adding the next.
Combine the milk and vanilla: Stop and scrape down the sides of the mixer. Combine the milk and vanilla in a measuring cup.
Alternate beating in the dry ingredients and milk mixture: Add 1/3 of the flour mixture to the mixer and combine on low speed. Stop and scrape down the mixer. Add 1/2 of the milk mixture and incorporate on low speed. Stop and scrape down the mixer. Add another 1/3 of the flour mixture to the mixer and combine on low speed. Add the remaining milk mixture and incorporate on low speed. Stop and scrape down the mixer, then add the remaining flour mixture.
Mix for 3 minutes on medium speed: Stop the mixer and give the whole bowl another good scrape. Get down to the bottom of the bowl where butter and sugar tend to hide and will make your cakes color and bake unevenly. Return the mixer to medium speed and beat until the batter is completely smooth, about 5 minutes.
Divide and color the batter: You'll be baking 2 or 3 cakes at a time, depending on the number of cake pans you have and what your oven will hold. You'll have about 4 pounds, 13 ounces of batter, so weigh out 12 1/2 ounces of batter (about 2 cups) into a small bowl. Add 1 teaspoon of gel food coloring and mix well with a rubber spatula. Pour the colored batter into a prepared cake pan. Repeat with another cake layer's worth of batter, a clean bowl, and another color of food coloring. If you have a third cake pan, repeat again with a third layer of cake batter. Cover the remaining cake batter with plastic wrap and set aside while baking the cakes; it's best if you only portion the batter you need at a time.
Bake the cakes: Bake the 2 to 3 colored cakes you have portioned and dyed until the cake is set, springs back when touched, and pulls away from the sides of the pan, 15 to 20 minutes.
Cool and wrap the cakes: Remove the cakes to a cooling rack and cool for about 30 minutes. Remove the cakes from the pans, keep the parchment paper on, and immediately wrap each still slightly-warm cake separately in plastic wrap. Set aside at room temperature.
Repeat dividing the batter, coloring it, and baking: Wash and dry your cake pans and line again with parchment rounds and cooking spray, set aside. Repeat dividing the batter, coloring it, and baking until all of the batter is used up. Cool and wrap the remaining cakes. Set aside at room temperature for up to 1 day.
Day 2: Make the frosting and build the cake
Beat the butter: Beat the butter in the bowl of a stand mixer fitted with a paddle attachment on medium speed until smooth.
Gradually add in the sugar: Turn the mixer speed to low and slowly add in the 7 cups of the sugar. Once it's all added in, increase the speed to medium-low and mix until thoroughly combined.
Add the liquid ingredients: Reduce the mixer to low, add in the cream or milk and vanilla, and mix until combined.
Whip until creamy: Once everything is incorporated, mix on medium speed until smooth and creamy.
Add the remaining sugar: Reduce the mixer speed to low and add in the remaining 1/2 to 1 cup of sugar until the buttercream is as firm as you want it. Turn the mixer back up to medium and whip again until fluffy.
Designate your cake layers: Stack the still-wrapped cakes and decide what order your rainbow will be. Designate which cakes will be the middle two layers. For our purposes, purple and blue will make the foundation of the cake, green and yellow the center, and orange and red the top two layers.
Build the foundation of the cake: Put a dab of frosting in the center of a cake or serving plate. Line the cake plate with 4 strips of parchment paper to keep the cake plate clean while you frost. Unwrap the purple cake layer and remove its parchment paper. If needed, use a long, serrated knife to level the cake. Place the leveled cake on the center of the cake plate. Top with 3/4 cup of frosting and smooth into an even layer. Some crumbs may stick into the frosting, but don't worry — you won't see them once the cake is complete. Unwrap the blue layer, remove the parchment, and level the cake. Invert the blue layer on top of the purple layer, making sure to align the two cakes as much as possible. Top with 3/4 cup of frosting and smooth into an even layer.
Make the filled layers: Unwrap the green layer, keep the parchment on, and level if needed. Use a 3-inch-wide round cutter to cut a hole in the center of the green cake layer and use an offset spatula to remove the small round of cake. Use the green cake's parchment paper to easily invert the green cake over the blue layer and align the cakes as much as possible. Remove the parchment paper. Frost the green ring with 1/2 cup of frosting, keeping clear of the hole. Repeat unwrapping, leveling cutting a hole, and placing yellow cake on top of the green cake. Remove the parchment and frost with 3/4 cup frosting, this time also frosting the interior of the cake's hole with a thin layer of frosting.
Fill the cake with sprinkles: Pour the sprinkles into the cavity in the green and yellow layers. Press the sprinkles in the sides and bottom of the cavity, being sure the center is quite full and packing in the sprinkles.
Make the final layers: Unwrap the orange layer, remove its parchment, and level if needed. Place the orange layer on top of the yellow cake layer and align with the other layers. Top with 3/4 cup of frosting and smooth into an even layer. Unwrap the orange layer, remove its parchment, and level if needed.
Invert the red layer on top of the orange layer and align the cakes as much as possible.
Crumb coat the cake and chill: Place 1/2 of the remaining frosting on top of the cake and use an offset spatula to spread it into a thin layer on the top and sides of the cake. Some crumbs will be picked by the frosting, but don't worry — you'll over those with another thin layer of frosting in a bit. Refrigerate the crumb-coated cake for 1 hour. Cover the remaining frosting with plastic wrap and set aside at room temperature.
Frost and decorate the cake: Top the chilled cake with the remaining frosting and spread into a thin, even layer on the top and sides of the cake. Top with any additional sprinkles, if desired.
Cut and serve the cake: Refrigerate the cake for at least 1 hour more or even overnight before slicing and serving. Use a long, sharp knife to slice through the finished cake, and be prepared that the tip of the knife will meet some resistance as it goes through the sprinkles.
- Make ahead: Bake the cake layers and store them at room temperature for up to 1 day.
- Storage: The assembled cake can be stored in the refrigerator for up to 5 days.