In a medium bowl combine cake flour, baking powder and salt and set aside.
Using an electric mixer cream together butter and sugar until light and fluffy. Add in eggs one at a time stirring after each addition. Stir in sour cream and vanilla until combined. Gradually add in flour mixture until combined.
Chill dough for at least one hour in refrigerator.
Preheat oven to 350 degrees. Line baking sheet with parchment paper.
Flour your work surface and using a floured rolling pin, roll out the dough so it is about 1/4 to 1/2-inch thick. Use a cookie cutter to cut out the cookies and place on the lined baking sheet about 2 inches apart.
Bake in preheated oven for 8-10 minutes or until the edges just begin to brown. Cool for a few minutes on baking sheet, and transfer to wire rack to cool completely.
Using an electric mixer combine butter and gradually add in confectioners sugar. When all sugar is added, pour in milk and vanilla and blend on medium until fluffy. Add in food color if desired.