Beat the egg whites in a large bowl. Gradually add one-fourth cup sugar until stiff peaks form. Set aside. Beat whole eggs (or egg substitute) with one-half cup sugar, the vanilla, lemon extract and lemon juice. Sift the flour and baking powder into the egg mixture and mix well. Fold 1 cup of beaten egg whites into the flour mixture and mix to lighten. Pour the batter into remaining beaten eggs whites and fold. Spray a 10-inch tube pan with a nonstick spray. Pour the cake batter into pan and bake in a preheated oven at 350 degrees for 35 minutes. Let cool 45 minutes before serving.