In a food processor, spin sugar about 2 minutes until it is superfine. Sift half of the sugar with the salt and the cake flour, setting the remaining sugar aside.
1 ¾ cups sugar, ¼ teaspoon fine grain salt, 1 cup cake flour, sifted
In a large bowl, use a balloon whisk to thoroughly combine egg whites, water, vanilla extract, and cream of tartar. After 2 minutes, switch to a hand mixer. Slowly sift the reserved sugar, beating continuously at medium speed. Once you have achieved medium peaks, sift enough of the flour mixture in to dust the top of the foam. Using a spatula fold in gently. Continue until all of the flour mixture is incorporated.
12 egg whites (the closer to room temperature the better), 1/3 cup warm water, 1 teaspoon vanilla extract, 1 ½ teaspoons cream of tartar
Carefully spoon mixture into an ungreased Angel Food Cake tube pan. Bake for 35 minutes, and check for doneness with a wooden skewer (when inserted halfway between the inner and outer wall, the skewer should come out dry).
Cool upside down on a glass bottle or a cooling rack for at least an hour before removing from pan.
To remove from the pan, gently go around the outside of the cake, inside the pan, with an offset spatula to make sure it releases. Use one hand to hold the pan and one hand to catch the cake. Jiggle the pan a little and it should release with no problem.