Preheat oven to 350.
Butter a 9x13 baking dish and set aside.
In a medium bowl, sift together the flour, baking powder, baking soda, and salt. Set aside.
Place the butter in your mixing bowl and cream the butter until smooth.
Add the sugar and continue to beat until the mixture is fluffy.
Add the eggs and beat until completely incorporated, scraping down the sides of the bowl as needed.
Mix in the sour cream and vanilla.
Gradually add the flour mixture, scraping down the sides of the bowl, beating until incorporated.
Pour the batter in the prepared baking dish, and set aside.