1 cup butter or margarine, softened
2 cups sugar
3 eggs
2 teaspoons grated lemon peel
1 teaspoon vanilla extract
3 1/2 cups all-purpose flour
1 teaspoon baking soda
1/2 teaspoon baking powder
1/2 teaspoon salt
2 cups sour cream
FROSTING:
3 tablespoons butter or margarine, softened
2 1/4 cups confectioners' sugar
2 tablespoons lemon juice
3/4 teaspoon vanilla extract
1/4 teaspoon grated lemon peel
1 tablespoon milk

In a mixing bowl, cream butter and sugar. Beat in eggs, one at a time. Add lemon peel and vanilla; mix well. Combine dry ingredients; add to creamed mixture alternately with sour cream (batter will be thick). Fill greased or paper-lined muffin cups with 1/4 cup of batter. Bake at 350 degrees F for 25-30 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes; remove to wire racks to cool completely. For frosting, cream butter and sugar in a small mixing bowl. Add lemon juice, vanilla, lemon peel and milk; beat until smooth. Frost cupcakes.

Source: allrecipes.com