All the sweet fruity flavors of rainbow sherbet in cupcake form. Raspberry, orange, and lime combine forces in both the cake and the buttercream frosting.
Slowly blend in the confectioners' sugar, cup by cup until well-combined. Mix in milk.
If you're using real raspberries instead of extract, place them in a saucepan over medium heat, stirring with a wooden spoon until they break down into a sauce. Continue to cook until sauce thickens. Remove from heat and pour through a fine mesh strainer. Press on seeds with wooden spoon to extract juice.
Mix 2 t fresh raspberry juice (or raspberry extract) into frosting in one bowl, mix orange extract into another, and mix fresh lime juice into the third.
If frosting is too stiff, more milk can be added 1 tsp at a time.