Bring egg whites to room temperature.
Add vanilla and vinegar to egg whites and beat until soft peaks form.
Add sifted sugar 1 tablespoon at a time.
Continue beating until very stiff peaks form and all sugar is dissolved.
Spread into three 9-inch round cake pans. Use pans with a blade scraper, or line pans with brown paper.
Bake at 300 degrees for 1 hour and 15 minutes.
Cool thoroughly in pans, then turn out.
Whip heavy whipping cream and powdered sugar (optional) until medium to stiff peaks form.
Spread whipped cream between layers and on top and sides.
Chill in refrigerator 12 hours or overnight.
Top with diced fruit before serving, if desired.