Preheat oven to 350º.
Lightly spoon flour into dry measuring cups, and level with a knife. Combine the flour, baking soda, and salt, stirring with a whisk.
Place sugar and butter in a large bowl; beat with a mixer at medium speed until well blended (about 1 minute). Add eggs, 1 at a time, beating well after each addition. Add banana, rind, and juice; beat until blended. Add flour mixture; beat at low speed just until moist. Stir in walnuts; spoon batter into an 8 1/2 x 4 1/2-inch loaf pan coated with cooking spray. Bake at 350° for 1 hour and 5 minutes or until a wooden pick inserted in center comes out clean. Cool 10 minutes in pan on a wire rack; remove from pan. Cool completely on wire rack.