Key Lime Frosting

1/4 cup butter
8 ounces cream cheese, room temperature
1 pound Icing sugar, sifted
2 TBSp key lime juice

Combine all ingredients in large mixing bowl; beat well until smooth. Makes enough cream cheese frosting for 24 cupcakes.

Key Lime Cupcake Filling

6 oz cream cheese softened
5 oz key lime juice
7 oz sweetened condensed milk

Place all ingredients in a mixer fitted with a paddle attachment. Mix on low for 30 seconds. Increase speed to medium and blend for 2 minutes. Place in a seperate bowl and place in fridge for 2 hours.

Take key lime pie filling and place into a pastry bag fitted with a small tip. Take tip and place into cupcake squeeze filling into cupcake. If you make large cupcakes, use the cone method.

Key Lime Pie Cupcake

2-1/4 cups self raising flour
1 tablespoon baking powder
1/2 teaspoon salt
1/2 cup butter, softened
1-1/2 cups sugar
4 egg whites
2 teaspoons vanilla
1 cup milk
zest of 6 key limes or 1 large lime

Preheat oven to 180°c
Grease and flour cupcake pans(or use liners). Combine flour, baking powder and salt in medium bowl; set aside. Beat butter and sugar in large bowl with electric mixer at medium speed until light and fluffy. Add egg whites, two at a time, beating well after each addition. Add vanilla; beat until blended. Add lime zest. With electric mixer at low speed, add flour mixture alternately with milk, beating well after each addition. Pour batter evenly into prepared pan.
3.Bake 20-22 minutes(for full size cupcakes) and 15 minutes(for mini) or until wooden toothpick inserted into centers comes out clean. Cool cupcakes in pan on wire rack 10 minutes. Remove from pan and allow to cool completely on rack.