Rainbow Layer Cake

"[ Photograph: Clare Barboza] Note: This cake is not difficult to make, but it is time-consuming and requires two batches of cake batter, so I'm not going to be bossy about what recipe you choose to use; instead, I am focusing on the process of how to assemble this lovely layered treat. You can use your favorite vanilla or yellow cake recipe (9x9-inch pan yield) or even two batches of cake made from a mix. I won't judge you, I promise. Additionally, since the cake demands a fairly large amount of frosting, depending on your mixer's capacity, you can make it in one big batch (as specified in the recipe) or halve the recipe and make in two batches...."