This was almost my biggest cake fail to date, you guys. I was watching the layers slide off of each other in slow motion at 12:30am with a 7am wake up call for hiking. I had used almost all of the icing and I was about to shrug off my 5-pack-of-tiny-cake-pans impulse buy when a certain dude came into the kitchen and carefully scraped the icing off each layer while I shaved each one flat with a serrated knife. I was still skeptical and Safeway had just closed so more icing wasn't an option, but we did it anyway and eventually the layers stopped sliding. The icing is still, clearly, sparse but I figured the sprinkles and colorful inside might detract from the pathetic icing job. I think this is a metaphor, but I could be wrong.
To recreate this bad boy, find yourself 5 mini cake pans (so as to only use one boxed cake mix), red, blue and yellow gel food coloring, colorful sprinkles and a package of vanilla icing--or to be safe, grab two. Split the batter evenly amongst the pans and dye each one a color of the rainbow. Clearly, indigo and violet didn't get any love in this rainbow, but if you can find seven pans that's even better.
Let all the mini cakes cool completely. I'm not so good with the patience, so this is hard for me but just do it. Once they are cooled, carefully shave the domes off the tops of each layer with a serrated knife and start icing. Stack them together, add more icing if you're not a dummy like me, and add sprinkles to the top.cake! Enjoy!