Gluten-Free Sugar Cookies with Lemon Frosting

Sift together flour, baking powder, baking soda and salt; set aside. 

In a large bowl, cream together 1 cup butter and 1-1/2 cups granulated sugar until smooth. Beat in the egg and sour cream until well blended. Stir in the sifted ingredients. 

Preheat oven to 375 degrees. Form dough into balls and roll in remaining 1/4 cup granulated sugar.  Press flat.

Bake for 8 to 10 minutes. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely. 

To make frosting, beat together remaining 1/4 cup butter, powdered sugar, lemon juice and water.  Frost cookies when cool.