Set the egg whites in bowl of mixer and let them come to room temperature.
When ready to cook, preheat oven to 350 degrees F.
Into a medium bowl, sift together the cake flour and powdered sugar; Set aside.
With mixer on medium speed, beat egg whites and cream of tartar until foamy. Increase mixer speed to medium high; beat until soft peaks form. Beat in salt, then gradually sprinkle in granulated sugar, 2 tablespoons at a time, and beat until egg whites stand in stiff peaks. Beat in vanilla and almond extract (if using).
Sift flour mixture, one-third at a time, into whites. Folding with a rubber spatula or wire whisk just until flour mixture disappears. Do no over-mix.
Turn batter into an ungreased 9 to 10 inch tube pan (highly recommend removal bottom tube pan). Bake 35 to 40 minutes, until cake springs back when lightly touched. Invert cake in pan and set on metal funnel or bottle. If using an angel food cake pan with legs, you won't have to worry about funnel or bottle. Let cool, then carefully loosen cake from side and center of pan.