In a large mixing bowl, mix flour, 1-1/2 cups sugar, baking powder, and salt. Make a well in center of dry mixture.
Add oil, yolks, peel, 1/2 cup juice, and water. Beat with electric mixer on low speed until combined. Beat on high speed for 5 minutes or until satin smooth.
Thoroughly wash the beaters. In a very large mixing bowl, beat egg whites and cream of tartar on medium speed until stiff peaks form (tips stand straight). Pour batter over beaten egg whites and gently fold in batter by hand.
Pour into an ungreased 10-inch tube pan. Bake in a 325 degree F oven for 65 t0 70 minutes or until top springs bak when you lightly touch it. Immediately invert the cake in pan and cool. Loosen sides of cake from pan and remove cake.
Prepare Orange Sauce and serve it with the cake.
In a medium saucepan, combine sugar, cornstarch, and salt. Stir in finely shredded orange peel and orange juice. Cook and stir the mixture over medium heat until its thickened and bubbly. Reduce the heat. Cook and stir for 2 minutes more. Remove from the heat. Gently stir in butter and lemon juice until the butter is melted. Cover the surface with plastic wrap. Cool slightly. Makes about 1-1/2 cups.