Preheat oven to 350°F. Grease 9x5-inch loaf pan. Combine sour cream and baking soda in small bowl. Using electric mixer, cream butter and sugar in large bowl. Beat in eggs, bananas and sour cream mixture. Sift in flour and baking powder. Stir in nuts. Spoon mixture into prepared pan. Bake until toothpick inserted into center comes out clean and loaf is golden brown, about 1 hour. Cool 10 minutes in pan. Turn loaf out onto rack and cool completely. bake 51