Sift flour once, measure, add baking powder and sift together three
times. Cream butter thoroughly, add sugar gradually and cream together
until light and fluffy. Add egg whites, 1/4 cup at a time, beating well
after each addition. Add flavoring and beat vigorously. Turn into two
loaf pans 9x5x3 inches, which have been greased, lined with heavy paper
and again greased. Bake in slow over (275 degrees F) 40 minutes; then
increase heat lightly (325 degrees F) and bake 40 minutes.
Source: The Latest Cake Secrets, General Foods Corporation, New York,
1934, pp. 52-53.