In a large mixing bowl, sift together 11/2 cups powdered sugar with salt, and cake flour. Setaside.
In another large mixing bowl, use a hand mixer to beat together egg whites, water, vanilla extract, vanilla extract, and cream of tartar. Whip for 2 minutes. Slowly include the remaining inch 1/2 cups of powdered sugar until stiff peaks form.
Sprinkle a number of this flour mix on top of the rigid egg peaks and gently fold in. Repeat this method to gradually fold all the remaining pasta mixture.
Scrape to an ungreased tube pan.
Bake in a 350-degree oven for 40 to 45 minutes, till the surface is lightly browned and is dry to your touch.
Remove pan from oven and immediately invert onto a cooling rack or simply by placing a bottle in through the center. Let cool in pan 11/2 hrs. Harness both sides and also bottom and gently remove the cake from the pan.