Surprise Rainbow Cake

November 25, 2011 · 3 comments

in dessert,food,recipe

A “surprise” rainbow cake is the perfect cake for a baby shower or a birthday party.  I should know, I made it for both events within the same week recently.  Crazy, I know!  But, it was so much fun to make!  And the results speak for itself.  :)

Yes, I know I typically stick with my cupcakes.  I do have a bias towards those serving-size delicious cuties, but I could not resist trying this adorable rainbow cake I recently saw on Martha Stewart’s site.   Instead of using the normal colors of the rainbow, however, I decided to use pastel colors for mine, which I thought would be fitting for a baby shower and a girlfriend’s birthday.

Shall we make some rainbow cake?

First, let’s start off by making the cake layers.

Make the batter first.  This is a simple white cake recipe, but you could also use any other batter.  Just make sure it’s close to colorless, so that the food coloring will turn out properly.  Some alternatives I think would work well are:  pound cake, coconut cake, lemon cake, poppy seed cake (though, don’t go overboard with the poppy for this cake).   You should have enough batter to make 2-3 normal 9-inch round cakes (~ 12 cups).

Divide the batter equally into 6 bowls.  You can use a weight scale here if you want to be exact, but I just eye-balled it.  I confess, and please don’t judge me, but I have never been a very exact cook.  I alter, combine and improvise a lot of recipes I find.  To me, that’s part of the fun in cooking/baking.  Plus, I personally think there are very few recipes where you need to be very exact with your ingredients.  With that said, I think anyone can make something delicious, even if they don’t end up following the recipe exactly.  :)

Okay, this is where the fun begins!  Using gel food coloring, make the following colors: purple, blue, green, yellow, orange and pink.  I recommend gel food coloring over the regular food coloring because the colors will be more vibrant.  Plus the color of the batter before baking will be about the same color as the final result, which will help you gage how much food coloring to put in the batter.

With shortening, grease the bottom of 6 pans, and then place a layer of parchment inside each pan (I traced and cut 6 out from a roll of parchment).  Grease the top of the parchment.  If you don’t have 6 pans, you can bake the layers one at a time.  I had two pans, so I bakes these layers in three batches.  Pour each bowl of batter in its own 9-inch round pan.  I recommend using an offset spatula to distribute the batter evenly in the pan.  This will ensure that the layers will be as even as possible, which will reduce or even eliminate the need to level the layers out later.

Once the layers are baked, let it cool a little before carefully removing the cake layers from the pan.  You will notice that the parchment between the pan and the cake layer will be very helpful at this point.   Wrap each layer individually in plastic wrap and put the layers in the refrigerator.  These layers can be stored in the refrigerator for several days, so they can be made ahead of time.  Even if you are planning on frosting the cake right away, keep the layers in the refrigerator while you make the frosting.  Chilled layers will be much easier to frost and your cake will be less likely to crumble into the frosting.

Next, you make the frosting.  I used a lemon meringue buttercream frosting, but you may certainty use whatever frosting you prefer.  I think a regular buttercream or cream cheese frosting would work just as well here.  A lighter frosting, such as whipped cream frosting may be a little difficult here because the light frosting will have less body and may not be strong enough to hold the six layers together, which could potentially make a mess.  But, I still think it’s possible, you will just need to be more careful when moving your cake, and I would suggest creating a slightly thicker whipped cream by adding a little more sugar than the recipe may call for.

Now let’s assemble the cake.  On a cake round, lay out some parchment strips, which will be on the bottom of where the edges of the cake will be.  This will make it easier to clean up the surface of the cake round after the cake is frosted.

Let the layering begin …

When the layers are complete, make the crumb coat.  This is the thin layer of frosting around the cake, which will help prevent any loose crumbs from mixing with the top layer of frosting.

Put the cake back into the refrigerator to allow the crumb layer to set.  This will make the top layer easier to frost.

Frost the top layer.  Once everything’s frosted, carefully remove the strips of parchment from the bottom edges of the cake.

I love raspberries and thought it’d look adorable on the cake.

Voila!  So cute!  You’d never guess there was a cuter surprised waiting inside. :)

The perfect cake for a surprise birthday party!

My favorite moment is when the birthday girl cut through the first slice and revealed the “surprise.”  So pretty!  Definitely a crowd pleaser. :)

A slice of the rainbow.

Not only was this cake adorable, it was really delicious.  It’s a must-try if you’re looking for a creative baking project. :)

For the baby shower, I used a little more batter for each layer so that the cake layers would be thicker.  Instead of raspberries, the cake was topped with adorable edible heart-shaped sprinkles.


Surprise Rainbow Cake

Original Recipe from Whisk Kid’s Super Epic Rainbow Cake

Makes one 6-layer 9-inch round cake


Six-Layer Rainbow Cake

  • Vegetable shortening
  • Parchment paper
  • 3 cups all-purpose flour
  • 4 teaspoons baking powder
  • 1/2 teaspoon salt
  • 2 sticks (1 cup) unsalted butter, room temperature
  • 2 1/3 cups sugar
  • 5 large egg whites, room temperature
  • 2 teaspoons pure vanilla extract
  • 1 1/2 cups milk, room temperature
  • Red, orange, yellow, green, blue, and purple gel food coloring

Lemon Swiss Meringue Buttercream

For the Filling and Crumb Coat

  • 9 large egg whites
  • 1 3/4 cups sugar
  • 2 cups (4 sticks) unsalted butter, cut into small pieces, room temperature
  • 2 teaspoons pure lemon extract

For the Frosting

  • 5 large egg whites
  • 1 cup sugar
  • 1 cup (2 sticks) unsalted butter, cut into small pieces, room temperature
  • 1 teaspoon pure lemon extract


Six-Layer Rainbow Cake

  1. Preheat oven to 350 degrees. Brush six 9-inch-round cake pans (or as many 9-inch cake pans as you have, reusing them as necessary) with shortening. Line bottom of each cake pan with parchment paper; brush again and set aside.
  2. In a large bowl, whisk together flour, baking powder and salt; set aside. In the bowl of a stand mixer fitted with the paddle attachment, cream together butter and sugar. Slowly add egg whites and mix until well combined. Add vanilla and mix until fully incorporated. Add flour mixture and milk in two alternating additions, beginning with the flour and ending with the milk. Mix until well combined.
  3. Divide batter evenly between six medium bowls. Add enough of each color of food coloring to each bowl, whisking, until desired shade is reached. Transfer each color to an individual cake pan. Use a rubber spatula and smooth out the batter so that the cake will be as level as possible to minimize the amount of trimming necessary.
  4. Transfer to oven and bake until a cake tester inserted into the center of each cake comes out clean, about 15 minutes (working in batches if necessary).
  5. Remove cake layers from oven and transfer to a wire rack; let cool for 10 minutes. Wrap the cake layers individually with plastic wrap and chill in refrigerator while making the frosting (below).
  6. Remove the cake layers from the refrigerator.  Using a serrated knife, trim tops of cake layers to make level, if necessary. Place four strips of parchment paper around perimeter of a cake round or lazy Susan. Place the purple layer on the cake plate. Spread a scant 1 cup buttercream filling over the first layer with a small offset spatula so it extends just beyond edges. Repeat process with blue, green, yellow, and orange layers.
  7. Place the remaining pink layer on top, bottom-side up. Gently sweep away any loose crumbs with a pastry brush. Using an offset spatula, cover the top and sides with a thin layer of frosting (also use any of the excess frosting visible between the layers). Refrigerate until set, about 30 minutes.
  8. Using an offset spatula, cover cake again with remaining frosting.

Lemon Swiss Meringue Buttercream

  1. Make the filling and crumb coat: Cook egg whites and sugar in a small saucepan over medium heat, whisking constantly until sugar is completely dissolved. Transfer to the bowl of a stand mixer fitted with the whisk attachment; mix on high speed until mixture is room temperature. With the mixer on medium-low, add butter, one piece at a time, mixing well after each addition.
  2. Remove whisk attachment and switch to paddle attachment. Increase speed to high and beat until buttercream comes together, about 5 minutes; beat in lemon extract.
  3. Make the frosting: In a clean saucepan and bowl of an electric mixer, repeat process in step 1.