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.
In the bowl of a stand mixer fitted with the whisk attachment, mix together the egg whites, water, extracts, and cream of tartar. Mix together for about 1 minute on low.
Slowly sift the reserved sugar in, 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.
Carefully spoon mixture into an ungreased tube pan.
Bake for 35 minutes before checking 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 cooling rack for at least an hour before removing from pan.
Video
Notes
Cake flour: Cake flour helps to make the cake nice and tender. If you don't have cake flour, this DIY cake flour recipe will help you how to make a good substitute.
Eggs: Using room temperature eggs will help the eggs to whip up better than using cold eggs.
Vanilla extract: I recommend using pure vanilla extract for the best flavor.
Almond extract: The extract adds a little something extra to the cake, but it's optional. Feel free to omit it if necessary.