Preheat the oven to 350°F.
In a food processor add the granulated sugar. Spin the sugar for 2 minutes until the sugar is very fine.
Sift half of the superfine sugar with the salt and cake flour. Set the other half of superfine sugar aside.
In a large bowl combine the egg whites, water, vanilla extract, and cream of tartar. Using a balloon whisk, thoroughly mix the ingredients together for 2 minutes. The egg mixer should become frothy.
Now switch to hand beaters; beat the egg mixture on medium speed, slowly adding the remaining sugar (that you set aside), until soft/medium peaks form.
Sift enough of the flour mixture over the top of the medium peaks mixture, just until the top has been lightly dusted. Using a rubber spatula, fold the flour mixture in. Continue doing this (lightly dusting the top of the egg mixture with sifted flour mixture) and folding it in until all the flour mixture is incorporated. Don't overmix, we want to keep as much air in the eggs as we can.
Scoop the cake mixture into an ungreased tube pan. Bake for 35 minutes.
Remove the cake from the oven and cool it upside down on cooling rack for 1 hour (cake still in pan) before removing the cake from the pan. Serve with fresh fruit and whipped cream.