Preheat oven to 450 degrees F. Beat egg whites until stiff; add sugar gradually, beating well after each addition. When egg whites are stiff and glossy, beat in cream of tartar, salt, and 1 teaspoon vanilla. Grease and sprinkle cornstarch over a 9x9-inch pan. Spread meringue in pan and set in oven. Immediately turn oven off; let meringue cook 4 hours, untended, then remove from oven. Whip cream until stiff; spread on meringue. Refrigerate 4 hours or more. To serve, cut into squares and top with crushed fruit mixed with remaining 2 teaspoons of vanilla.