This isn't the first (or even the second) time I've made an "epic" rainbow cake for someone's birthday, but I usually do save it for a significant milestone. Madeline's 5th, Sharon's 60th, and now Jamie's 40th. Jame's was the tallest cake yet since we did the full Roy G. Biv of rainbow colors, plus a pink layer on the bottom. Eight layers of goodness, especially since I used the vanilla cake recipe from Smitten Kitchen! It was delicious, sturdy, and worked well with all my colors. I used this recipe for the frosting (always delicious).