Rainbow Cake

Every month at the Campus Food Bank we have a birthday cake day for all the volunteers who celebrate their birthdays that month! I was in charge of making this month's birthday cake and couldn't wait to try out this rainbow cake idea I've had in my head for a while. I had also considered making a St. Patrick's Day themed cake and but I figured that rainbows are also pretty thematic for this time of year. The best part about this cake is the surprise rainbow layer inside! It's a great birthday cake, and I think it would be perfect for a child's party or even Easter.

Rainbow Cake Ingredients:

1 box Rainbow Bits cake mix - This will make the top and bottom layers of your cake. To make the box mix more moist I use buttermilk in the place of the water or milk that the instructions call for.

 Mini marshmallows

Sour rainbow candy strips

1 tube white decorators icing

Vanilla Rainbow Cake Layer

1/2 cup unsalted butter, room temperature

1 cup white sugar

3 large eggs

1 and 1/2 tsp. vanilla extract

1 and 1/2 cups all purpose flour

1 and 1/2 Tbsp. baking powder

1/8 tsp. salt

1/2 cup buttermilk - Make your own buttermilk by combining 1/2 Tbsp. of white vinegar with enough milk to make 1/2 cup

Red, blue, yellow, and green food colouring

Directions: 

Bake the Rainbow Bits cake according to the directions for two 9" round cakes on the package. I line the bottom of my round cake pans with a circle of parchment paper and spray them with non-stick cooking spray for easy removal of the cakes after baking. Once they are done baking, allow them to cool completely on wire racks while you make the vanilla rainbow cake layer.

For the vanilla rainbow cake layer: Preheat the oven to 350 degrees F. Line the bottom of a 9" round cake pan with a circle of parchment paper and spray with non-stick cooking spray.

In a medium bowl, cream together the butter and sugar with a mixer. Add in the eggs and vanilla extract and continue to mix until well combined. In a separate bowl, whisk together the flour, baking powder, and salt until combined. Add the flour mixture into the wet ingredients in three additions, alternating with adding in the buttermilk, mixing well between each addition. Scrape down the sides of the bowl as necessary.

Once the vanilla cake batter is prepared, evenly separate it into four bowls. Dye each bowl of vanilla cake one of the four colours of food colouring, by adding in a few drops of colour and stirring.

Create the rainbow effect by pouring a small amount of one colour of batter into the bottom of the prepared cake pan, then adding in another beside it, and so on. Continue pouring small amounts of different coloured batters on top of one another (as pictured below) until all the batter has been used.

Bake in the preheated oven for 28-30 minutes, or until a toothpick inserted into the middle of the cake comes out dry with a few crumbs attached. Remove from the oven and allow the cake to cool completely on a wire rack before assembling and icing the cake.

Cream Cheese Icing Ingredients:

1 cup cream cheese, room temperature

1 and 1/4 cup butter, temperature

7 cups icing sugar

2 Tbsp. vanilla extract

1 Tbsp. milk

Blue food colouring - I used Royal Blue Wilton gel paste

Icing Directions:

In a stand mixer or with using in electric mixer, cream together the cream cheese and butter until smooth. Add in the vanilla extract and mix until incorporated. Slowly add in the icing sugar, 1 cup at a time, scraping down the sides of the bowl as needed. Add in 1 Tbsp. of milk if needed to reach the desired consistency. Mix in the blue food colouring until the icing is bright sky blue. If you are making the icing ahead of time then in mind that the icing colour will intensify the longer you leave it to sit.

This recipe should make more icing than you will need to ice this cake, but I always like to have too much rather than not enough icing I just freeze whatever is leftover in an airtight container to use for other cakes or cupcakes.

Assembling and Decorating the Cake:

Begin by levelling off all of your cake layers with a sharp, serrated knife so that they are completely flat on top. If your cakes are already level then skip this step. Place one of the Rainbow Bits layers right-side up on your serving platter or plate, and spread out a thick layer of cream cheese icing on top.

Place the vanilla rainbow cake layer on top of the icing and spread another thick layer of cream cheese icing on top. Place the second Rainbow Bits layer, top-side down on top of the vanilla rainbow cake layer.

Put a large amount of the cream cheese icing in the middle of the top cake layer. Smooth over the top of the cake and down the sides with an angled spatula or knife. Finish evenly icing the cake with the remaining cream cheese icing.

To decorate the cake, I used sour rainbow candy strips to make a rainbow, then made small "clouds" with mini marshmallows. I placed a small amount of icing on the bottom of each marshmallow before I pressed it onto the cake so that they would stick on. I used more of the rainbow candy strips to decorate the sides of the cake by placing a small amount of icing on the back and wrapping them around the bottom, middle, and top of the cake. I piped the border and the "Happy Birthday" on using a tube of storebought white decorators icing that you can attach an icing tip onto.

Here is what the inside of the cake will look like when you cut into it! Each piece will have a different looking rainbow slice in the middle!

*Recipe by Brooke McMillan