In a mixing bowl, combine egg whites, vinegar, vanilla and 1/8 tsp salt. Beat until soft peaks form. Gradually add 1 cup sugar; continue beating until stiff peaks form. Cover baking sheet with plain brown paper. Spoon egg white mixture into eight mounds on paper. Shape into cups with a spoon. Bake at 300 for 35 minutes. Turn oven off; let shells dry in oven at least 1 hour with the door closed. Remove shells from paper. When thoroughly cooled, store in an airtight container. For custard, combine cornstarch and remaining salt and sugar. Add water and mix well. Cook and stir until thick and bubbly, about 2 minutes. Beat egg yolks; add a small amount of hot mixture. Return to saucepan. Cook and stir 2 minutes longer. Remove from the heat; blend in lemon peel, juice and butter. Chill. Just before serving, fill meringue shells with custard and top with whipped cream.
