Line a loaf pan with plastic wrap. Spread 1 pint softened vanilla ice cream in the pan; freeze until hard, 1 hour. Spread with 1 pint softened orange sherbet; freeze 1 more hour. Top with a layer of pound cake slices; freeze at least 1 more hour. Beat 4 egg whites and 1/2 teaspoon lemon juice with a mixer until frothy, then beat in 1/3 cup sugar until stiff. Invert the ice cream loaf onto a baking sheet, remove the plastic wrap and cover completely with the meringue. Bake at 500 degrees F until browned in spots, 3 minutes.