Butter Cake

2-1/4 cups sifted cake flour1-1/2 cups sugar3 tsp. baking powder1 tsp. salt1/2 cup cooking (salad) oil5 unbeaten egg yolks (medium)Juice of 2 medium oranges plus water to make 3/4 cup grated rind of 2 oranges (about 3 tbsp.)1 cup egg whites (7 or 8)1/2 tsp. cream of tartar Heat oven to 325 F, Sift flour,…