Preheat the oven to 350°. Butter and flour a 9-inch-round springform cake pan. In a medium bowl, whisk together the flour, sugar, baking powder, baking soda and salt. Using an electric mixer at low speed, beat in the butter until it looks like coarse meal. In a small bowl, whisk the egg yolks with the sour cream and vanilla. Beat the egg mixture into the dry ingredients at medium-low speed just until incorporated, about 1 minute. Scrape the cake batter into the prepared springform pan.