In large bowl beat first 5 ingredients until well blended. Stir in sour cream. In a separate bowl stir together dry ingredients. Add to sour-cream mixture and beat until well blended. Stir in diced prunes.
Scrape batter into a greased and lightly floured 4-½x8-½-inch metal loaf pan. Shake pan gently to smooth out top of batter. Bake at 325 degrees F until sides begin to pull away from pan and toothpick inserted in the center comes out clean, about 75 to 90 minutes. Let cool in pan 10 to 15 minutes, then turn out onto rack to finish cooling. Eat warm, at room temperature, or toasted.