Separate egg whites and leave sit at room temperature for at least an hour.
Pre-heat oven to 350 degrees.
Sift together flour and ¾ cups sugar, sift 4 times, set aside.
In large mixing bowl combine egg whites, cream of tartar.
Beat on medium speed until egg whites hold a soft peaks, about 2 minutes. Do not over beat.
Add salt and vanilla, beat to combine.
Turn mixer to medium high and gradually add in 1 cup of sugar. Do this by quickly, but gradually. Beat until stiff glossy peaks form. Scrap sides down as needed. About 2 minutes.
Remove bowl from mixer and using rubber spatula gently fold in flour and sugar, mix until well combined, but don't over mix.
Gently spoon batter into large angel food cake pan. (do not grease pan!!)
Cut a knife or spatula through batter to remove air bubbles.
Bake 350 degrees for about 35-40 minutes, until top is golden brown. (top should have dry looking cracks and spring back when gently pushed.
Remove from oven and immediately invert until cool.
Run a knife around inside of pan and tube to release sides of cake. Remove, then run knife through to release bottom of cake from pan.
Decorate with favourite icing or serve plain with fresh berries and whipped cream.