Happy St. Patrick’s Day! I have a rainbow cake for you today! I love St. Patrick’s Day, and celebrating my Irish heritage. With all the bright, happy colors this cake has to offer, it is perfect for any occasion. You start with a basic white cake recipe, but this cake does take some time to make. You want to allow time to tint each layer of color, and if you are using a small pan like I did, and you only have one, it will take a bit longer. Definitely start a couple days ahead of when you want to serve it. 
Rainbow Cake
Cake
2 cups Flour
1 teaspoon Baking Powder
1/2 teaspoon Baking Soda
1/8 teaspoon Salt
1/2 cup Butter
1 3/4 cup Sugar
1 teaspoon Vanilla
4 Egg Whites
1 1/3 cup Buttermilk
Buttercream Frosting
1/2 cup Shortening
1/2 cup Butter
1 teaspoon Vanilla
4 cups sifted Confectioner’s Sugar
2 tablespoon Milk
Royal Icing
3 oz. Warm Water
2.5 tablespoons Meringue Powder
1/2 teaspoon Cream of Tartar
1 Confectioner’s Sugar
Also Needed
4″X 2″ round cake pan
Pan Spray or shortening
flour
big skewer, taller than the cake
cake/frosting colors-red, orange, yellow, blue, green, purple
Preheat oven to 350 degrees
This is the pan I used. It is a 4×2 from Wilton. Grease and flour the pan.
Mix together the flour, baking powder, baking soda, and salt in a bowl. Set aside. Beat the shortening and butter together for 30 seconds. Add sugar, and vanilla. Add egg whites, one at a time. Add flour mixture and buttermilk, a little at a time, alternating between the two, until it is all mixed together.
Take 2/3 of a cup of the batter and tint it with a decorator color. Pour into pan and bake for 15-20 minutes. Let cool. Then remove from pan. Continue until all the layers are baked. Make buttercream frosting.
Before you begin frosting, level off each cake piece so it is even and they are all the same height. Use a large round tip (Wilton M1) and a pastry bag filled with the white buttercream. Start with the bottom piece of cake and cover the top of the cake with the buttercream in a circular motion. Continue frosting and stacking each cake piece until it looks like above, except frost the top piece also.
Put a crumb coat, a first layer of white buttercream frosting on your cake, and refrigerate it.You may want to place the skewer down the center of the cake at this time. Once chilled, remove from fridge and frost with another layer of white buttercream. Refrigerate. Don’t worry if it is not perfect looking. You will be adding the colored strings of icing next, which will draw attention to the colors, not the white frosting.
Make your royal icing by whisking together the warm water and the meringue powder for 30 seconds. Use a mixing bowl than you want to mix the entire recipe in.Then add in the cream of tartar and whisk for 30 seconds again. Put the bowl on your mixer and add confectioner’s sugar. Mix on lowest speed for 10 minutes. This is a half recipe, and it will still make more than you need, but this recipe is perfect for decorating cookies too!
Place a little bit of royal icing in 6 different bowls, and color each one the same as the cake layers.
Start drizzling the colors however you want. Refrigerate until ready to cut.
Thanks for joining me today!
