How to Make a Rainbow Reveal Cake

Whether you are celebrating a first birthday or a 99th birthday, this insanely clever cake will surprise your whole party.

By: Beth Klosterboer

Related To:

The Ultimate Birthday Surprise

No matter how old you are, the excitement of cutting into a birthday cake never dulls with age. But this year, why notreally surprise the birthday guy or gal with a cake that completely ups the ante? Once the cake is cut, each slice reveals the guest of honor's age in the middle of a bursting rainbow of color. And though it looks complicated to make, the process is actually simpler than you think — just take it step by step.

Get the Recipe: Tie-Dye Rainbow Reveal Cake

Make the Chocolate Batter

Prepare the batter for the cake's numbers according to the recipe instructions. Line a 13-by-5-inch loaf pan with aluminum foil, spritz it with a little nonstick cooking spray, and pour in the batter.

Bake It

Bake at 350 degrees F until a toothpick inserted in the center of the cake comes out clean, about 52 to 58 minutes.

Cool, Cut and Freeze

Cool the cake in the pan for 10 minutes, then remove it and allow it to cool completely on a cooling rack. Cut the domed top off the cake and 1/4 inch off each end. Slice the cake into 13 equal slices (they'll each be 1 inch thick), and freeze the slices for 1 hour.

Remove from freezer, then cut out numbers from each slice using small (1 3/4-inch) cookie cutters. To remove the cake from the cookie cutters, use a wood dowel to gently push the pieces out.

Freeze Again

Keep cutting out numbers until you have 13 sets. Then, pop them back into the freezer (covered, on a baking sheet or cutting board lined with a silicone mat, aluminum foil or parchment) for 1 hour.

Prepare the Tie-Dye Batter

Create a second batch of cake batter (this time, a white cake) according to the recipe instructions. Equally divide the batter among 7 bowls. Using food coloring, color one bowl purple, one royal blue, one sky blue, one green, one yellow, one orange and one red.

At this point, you can preheat the oven to 350 degrees F again. Line a 13-by-5-inch loaf pan with aluminum foil sprayed with nonstick cooking spray.

Start by Piping

Pour each colored batter into a disposable pastry bag or large zip-top bag, with a corner snipped off.

Remove the cake numbers from the freezer. If any of them have holes (like the 6 here), pipe in two different batter colors, filling the hole two-thirds full. Then, pipe some squiggles of purple batter into the bottom of the pan, leaving room for other colors in between the squiggles. Pipe another color on top, then another and another, until you've piped all 7 colors into the bottom of the pan in a thin layer.

Add the Numbers

Gently stand and press the cake numbers into the batter, in a neat row that goes down the whole pan. Pipe squiggles of colored batter in between and around the numbers, switching up the colors as you go.

Smooth Out the Top

Finish up by piping the colored batter on top of the numbers. Smooth out the top of the cake, but be careful not to mix the colors together, or the cake will look muddy. Tap the pan on the counter five times to help remove big air bubbles.

Bake and Shape

Bake the cake for 55 to 60 minutes, until the top turns deep brown. Insert a long toothpick in the center. If it comes out clean, the cake is done. Cool the cake in the loaf pan for 10 minutes, then remove and set on a cooling rack to finish cooling completely. Slice off the domed top and about 1/4 inch off each end to create straight sides.

Prep the Icing

Prepare the marshmallow creme frosting and frost the cake according to the recipe instructions. Then, you can move on to the rainbow glaze.

Combine 3 ounces finely chopped white candy melts, 3 tablespoons heavy whipping cream and 1 1/2 tablespoons corn syrup in a microwave-safe bowl. Microwave on high in 15-second increments, stirring after each, until melted. Divide the glaze equally among 7 small bowls. Color one purple, one royal blue, one sky blue, one green, one yellow, one orange and one red.

Get Drippy

Allow the glaze to cool and thicken slightly. Then, create a melting rainbow by pouring colored glaze down the side of the cake in a rainbow. Set the cake on a serving dish — and remember which end will show the numbers facing forward!

Slice and Serve

Step back and watch as the birthday honoree cuts the first slice. Everyone will be delighted to see the numbers set on a swirling tie-dye backdrop.

On Tonight

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