Preheat oven to 350°. Butter and lightly flour 8 x 4 inch loaf pan. Sift SWANS DOWN Cake Flour and lightly spoon into measuring cup for 1 ¾ cups. Add baking powder, salt and baking soda; sift again and set aside. Cream butter and sugar, add eggs; beat well. Stir in nuts and grated orange zest. Add flour, alternately with bananas, a small amount at a time, beating only until smooth after each addition. Pour into prepared pan. Bake for 55 minutes. Store air tight 6 hours before serving.