Preheat the oven to 350°F and grease your cake pan and line it with parchment paper. Prepare 6 different-colored cakes according to the recipe and bake each cake for 40 minutes.
Let the cakes cool and level off the top, bottom, and sides of each cake so that they are all uniform.
Use the larger cake ring to carve out a circle in each cake.
Now use the smaller cake ring to carve out a smaller circle inside the first circle of each cake.
Swap out the small circles in the cakes, as shown in the video.
Now swap out the large circles in the cakes, as shown in the video.
Prepare the frosting and spread some over each cake.
Stack the cakes on top of one another, with the frosting side up, and coat the entire cake with the rest of the frosting. Decorate the cake with the rainbow toppings of your choice.