Intense Chocolate Bread

Preheat oven to 350. Grease a 9x5x3 inch loaf pan. In a large bowl beat the butter,sugar and vanilla with an electric mixer on high speed until pale and fluffy. Scrape down sides of the bowl ; beat in the eggs one at a time. Add cocoa, sour cream, baking powder, baking soda and salt; mix at low speed. When ingredients are well blended scrape down sides of bowl. Add flour; mix only until blended. Spread the batter in the pan. Bake until a toothpick comes out clean, about 60 to 70 minutes. Place the pan on a wire rack to cool for 30 minutes. Loosen edges of bread with a knife and invert onto the rack. Turn bread over and let cool completely. Dust with powdered sugar.