In another clean, grease-free bowl, whip the egg whites until they have tripled in volume and are light and foamy. With the machine running, add the 3 tablespoons of sugar, salt and continue to whip until the egg whites are stiff, but still shiny. Fold the egg whites into the batter and pour it into the prepared cake pan. Immediately place the cake in the center of the oven, and bake for approximately 20-30 minutes, or until the center springs back when gently pressed.