Preheat oven to 350°F (175°C) and grease two 8-inch cake pans.
Cream butter and sugar together until pale and fluffy.
Beat in eggs one at a time, then stir in vanilla bean paste and sour cream.
Whisk together flour, baking powder, and salt in a separate bowl.
Alternate adding dry ingredients and milk to the wet mixture, starting and ending with flour.
Divide batter evenly between pans and smooth the tops.
Bake for 30-35 minutes until a toothpick comes out clean.
Cool in pans for 10 minutes, then transfer to a wire rack.