Royal Velvet Chiffon Cake
["1 2/3 c. cake flour, sifted", "1 3/4 tsp. baking powder", "1 tsp. salt", "1 c. sugar", "1/3 c. salad oil", "2/3 c. juice from 2 medium oranges and water", "2 Tbsp. orange rind, grated", "5 egg yolks (1/3 c.), unbeaten (reserve egg whites)"]
["Sift together dry ingredients.", "Add wet ingredients and beat until smooth.", "Beat 5 egg whites (2/3 cup) with 1/4 teaspoon cream of tartar until egg whites are stiff, but not dry.", "Add 1/4 cup sugar gradually; beat to a very stiff meringue.", "Do not underbeat. Fold egg yolk mixture carefully into egg whites until completely blended.", "Pour into ungreased 9 or 10-inch pan.", "Bake in moderate oven (350\u00b0) for 50 to 60 minutes for 9-inch pan; 40 to 50 minutes for 10-inch pan.", "Cool in inverted pan about 1 hour."]
["cake flour", "baking powder", "salt", "sugar", "salad oil", "oranges", "orange rind", "egg yolks"]