In the bowl of a standing mixer (or with a hand mixer) cream the butter until light and fluffy, about 1-2 minutes.
Add in granulated sugar and brown sugar. Cream the mixture until light and fluffy, about 1-2 minutes.
Add in the eggs, one at a time, beating well after each addition.
In a separate bowl, sift all purpose flour, baking powder, baking soda and salt together.
Alternately, beginning and ending with the flour mixture, add in the flour mixture and the buttermilk. Mix until just combined.
Add in the sour cream and vanilla, mixing until well combined.