In the bowl of an electric mixer fitted with the paddle attachment, beat the butter for 1 minute, or until creamy. Add the sugar and beat for 2 to 3 minutes more, or until the mixture is light in color. Add the eggs, one at a time, beating on low speed after each addition and scraping down the bowl with a spatula as necessary, until they are incorporated. Add the sour cream and vanilla and mix until combined. With the mixer on low speed, gradually add the flour mixture and beat just until combined.