Add the cream of tartar to the egg whites and beat until stiff.
Add the sugar, one tablespoon at a time, as you continue beating
the egg whites. Beat in the salt and the vanilla. Spoon the
mixture into a buttered 6x8 inch pan and place in a preheated 450
degree oven and immediately turn off the heat. (You may want to
make shallow indentations, or wells, in the surface of the meringue
to hold the topping when you serve it.) Leave the cake in the oven
overnight or until the oven has completely cooled. Serve with your
choice of ice cream, berries, and/or whipped cream.
Serves 4 to 6.