Increase oven temperature to 450°F. In 1-quart saucepan, mix sugar, 1/4 cup water and the salt. Cook over medium heat, stirring just until sugar dissolves. Heat to boiling. Boil about 8 minutes, without stirring, to 238°F on candy thermometer; remove from heat. In medium bowl, beat egg whites and cream of tartar with electric mixer on high speed until soft peaks form. Pour hot sugar syrup in thin stream over egg whites, beating until stiff peaks form. Beat in vanilla. Spoon meringue into decorating bag fitted with open #6 tip. Pipe meringue onto cupcakes. Place cupcakes on cookie sheet. Bake 2 to 4 minutes or until lightly browned.