Adapted from Bon Appetit via [My Madison Bistro|http://mymadisonbistro.com/archives/key-lime-cupcakes]
Yields: 1 two-layer 9 inch round cake
Preheat oven to 350. Grease and flour two 9-inch round cake pans.
Sift the cake flour, baking powder, baking soda, and salt. Set aside.
Using a mixer fitted with the paddle attachment, beat the butter on low until it’s softened a bit. Add the sugar and increase the speed to medium. Beat until fluffy, about four minutes. Add one egg at a time, beating well after each addition. Add the lime juice, zest, and food coloring and beat until mixed. (The mixture will look curdled.)
Add the flour in three additions, alternating with the buttermilk, beginning and ending with the flour, scraping down the bowl as necessary. Mix on low until just combined.
Divide batter evenly between two pans and spread flat with an offset spatula.
Bake 25 minutes. Cool completely and frost with cream cheese icing.
!For Frosting:
Beat the butter and cream together vigorously until combined and fluffy. Gradually add the powdered sugar on a low speed until the consistency you desire is achieved. If using, fold in zest and food color.