Banana Chiffon Cake
["5 egg yolks", "1 c. egg whites (7 or 8)", "2 c. sifted flour", "1 1/2 c. granulated sugar", "3 tsp. baking powder", "1 tsp. salt", "1/2 c. salad oil", "1 c. mashed ripe banana (2 or 3)", "1 Tbsp. lemon juice", "1/2 tsp. cream of tartar"]
["Let yolks and whites warm to room temperature.", "Start heating oven to 325\u00b0."]
["egg yolks", "egg whites", "flour", "sugar", "baking powder", "salt", "salad oil", "mashed ripe banana", "lemon juice", "cream of tartar"]