Preheat oven to 350 degrees.
Sift together flour, baking powder, baking soda and salt.
Beat together butter and sugar in large mixing bowl fitted with a paddle attachment until light and fluffy.
Add eggs, one at a time, beating well after each addition, then beat in vanilla.
Add half the flour mixture and mix on low speed until just blended, then add sour cream, mixing until just combined. Add remaining flour mixture and mix at low speed until batter is smooth.
Fill paper baking cups about 2/3 full and bake 15-17 minutes until toothpick comes out clean. Take care to not overbake.
Cook completely before frosting.