Sift flour, salt and baking powder together.
Cream butter and sugar well. Add the water and mix. Add the sifted flour, salt and baking powder. Fold in egg whites, then beat hard for 5 minutes with a hand beater.
Line a loaf pan (9×5×3) with buttered waxed paper. Cover with a layer of crumbled geranium leaves. Pour batter over the leaves.
Bake in a moderate oven, preheated to 375 degrees, about 50 minutes. When removing waxed paper, don't worry about the fact that the leaves pull off the cake with the paper. They are for flavor in this case, not for decoration. Shake powdered sugar through a paper doily oven the cake.