Preheat oven to 350 degrees F (180 C). Grease bottom and sides of 9 x 5 or 8 1/2 x 4 1/2-inch loaf pan with margarine; line bottom of pan with parchment paper and generously grease paper with margarine.
In a large mixing bowl, sift together flour, baking soda, baking powder and salt. Set aside.
With an electric mixer, beat the margarine; add the sugar and beat well, until mixture is fluffy. Add applesauce, vanilla, and bananas. Mix well.
Fold in (by hand) the dry ingredients and nuts (if using).
Place batter in prepared loaf pan and bake in preheated 350 degree F (180 C) oven for 55-60 minutes. Loaf is done when top is golden and cake tester inserted in center of loaf comes out clean. Transfer pan to wire rack, let bread cool in pan for 10 minutes; loosen sides with knife, then invert and cool bread on rack completely. Slice and serve when cooled completely.
Makes 1 loaf, 8-10 good size slices.
Date: January 3, 2003