Preheat the oven to 325°F. Cream together butter and sugar until light and fluffy. Add vanilla and salt; mix well. Sift together flour and cornstarch and add to the creamed mixture. Blend well. Form dough into 1” balls and place on a parchment-lined cookie sheet 2” apart. Flatten each ball with a fork and place half a glace cherry on top of each cookie. Bake for 10-12 minutes, or until the edges just start to turn very light golden. Makes 2 dozen cookies.