1Bring butter, eggs, and sour cream to room temperature. Grease and lightly flour an 9 x 5 x 3 inch loaf pan. In a medium bowl stir together flour, baking powder, and, baking soda .Set aside. In a large bowl beat butter with an electric mixer on medium to high speed about 30 seconds or until softened. Gradually add sugar, 2 tablespoons at a time, beating on medium to high speed about 6 minutes total, or until very light and fluffy. Add vanilla. Then add eggs, one at a time, beating on low to medium speed for 1 minute after each addition; scraping sides of bowl often. Alternately add the flour mixture and sour cream beating on low speed just until combined.Spread batter in the prepared pan. Bake in a 325F oven for 1 to 1 14 hours or until cake test done. Cool cake in pan on a wire rack for 10 minutes. Remove cake from pan and cool completely. Sift powdered sugar over the top.