Into a medium mixing bowl sift together the flour, sugar, baking powder and salt. Make a well in the center; add corn oil, egg yolks, banana, orange rind, and orange juice. With a wooden spoon beat until smooth. In a large mixing bowl beat egg whites and cream of tartar until whites hold stiff peaks when beater is slowly withdrawn. Gently fold in flour mixture, blending well. Pour into an ungreased angel food cake pan 10 x 4 inches. Bake in a preheated 325 degree oven until a cake tester inserted comes out clean and cake springs back when touched 1 hour and 10 or 15 minutes. At once invert pan and let stand on legs; if pan does not have legs invert over a funnel or bottle; cool completely. With a small metal spatula loosen edges and around tube; ease out of pan with fingers. Leave cake bottom side up (top will have cracks) and cover with Orange Frosting. Cake my be cut into 15 (2-inch) wedges.