Sift sugar with flour, cocoa, and salt.In a separate bowl, whip egg whites, lemon juice, and vanilla until peaks form. Add sugar and whip until peaks are stiff. Gently fold in sifted dry ingredients in 2 parts. Pour batter into an ungreased bundt or cake pan.
Bake at 325*F for 45-55 min or until cake springs back when touched. Cool upside down on a cake rack, slice and serve.