Rainbow Cake

I just made this cake for my mom's birthday. The original recipe comes from Whisk Kid, who has some lovely creations.  Instead of making the recipe entirely from scratch, I used 3 white cake mixes, Betty Crocker gel food colors (which were way cheaper), and my own frosting recipe.

3 white cake mixes
eggs
vegetable oil
water
Food color gel
Six 9 inch round cake pans (or as many as you have, reusing them if necessary)
Parchment paper
White frosting

Mix cake and preheat oven as directed on the package. Grease each cake round with shortening.  Line the bottom of each cake pan with parchment paper, grease again, and set aside.  Place 2 1/2 cups of cake mix into six separate bowls.  Add food color gel to each bowl to create the colors desired (red, orange, yellow, green, blue, purple).  Transfer each color batter to a separate cake round.  Bake as directed on the package.  Allow cakes to cool in pans for 10 minutes then cool completely on a wire rack.

Make frosting while cakes cool.  If you use my recipe triple it for the entire cake.

Using a serrated knife, trim the rounded tops from each cake until level.  Using a cake pedestal put a dollop of frosting in the center to cement the purple layer (bottom side up) to the dish.  Frost purple layer just so the frosting extends slightly over the edge, top with blue layer.  Repeat for all layers.  Cover the top and sides with frosting (this is the rough frost, it doesn't need to be crumb free).  Refrigerate the cake about 30 minutes (not the remaining frosting).  Once the cake is chilled and the frosting is set, frost the cake again with the remaining frosting.

Photo Credit