1 lb. butter
3 c. sugar
10 eggs, separated
5 1/2 c. all purpose flour
6 tsp. baking powder
2 tsp. vanilla extract
1 tsp. grated lemon rind

Beat 1 pound (4 sticks) very soft butter with 3 cups of sugar for 5 minutes at low speed. Add 10 egg yolks and beat 2 minutes at low speed. Beat 10 egg whites at high speed with same beater. Then beat creamed mixture 5 minutes longer at low speed. Sift 5 1/2 cups sifted all purpose flour and 6 teaspoons baking powder together. Beat 1/3 flour into bowl at low speed. Beat in 3/4 cup milk until smooth. Beat in 1/3 of flour until blended. Add egg whites and beat until smooth. Reserve 1/4 flour. Add remaining flour to bowl. Increase speed to medium and beat for 5 minutes.

Grease 1 (9") and 1 (10") tube pan generously. Coat evenly with reserved flour, tapping excess into bowl. Add 2 teaspoon vanilla and 1 teaspoon grated lemon rind. Beat at medium speed 2 minutes. Pour batter in prepared pans. Bake in slow oven, 300 degrees for 1 hour and 15 minutes or until center springs back when lightly pressed with fingertips. Cool in pans on wire rack 10 minutes. Loosen around sides and tube of pan with a knife and insert cake onto wire rack to cool completely.