Preheat oven to 350 degrees F.
Spray a tube pan with non-stick spray.
Beat egg whites until foamy.
Gradually add cream of tartar and continue to beat until soft peaks form.
Gradually beat in 1 cup sugar very slowly until mixture holds stiff peaks.
Fold in vanilla extract.
Combine flour, cornstarch, 3/4 cup sugar, and salt in a small bowl. Slowly fold into egg whites.
Add batter to 10-inch tube pan and level the top with a spatula.
Bake at 350 degrees for 40 to 45 minutes or until the top springs back when touched with your finger or a wooden pick inserted near the center comes out clean.
*Very important - Invert pan over a bottle and let stand until cake is completely cool. when cool, loosen sides and center with a metal spatula and turn ou onto a platter.