Coat 2 large baking sheets with cooking spray, and dust with 1 tablespoon flour; set aside. Combine sugar, cornstarch, margarine, and egg in a large bowl; stir well with a wire whisk. Scrape seeds from vanilla bean; addseeds to sugar mixture, reserving bean for another use. Add 3/4 cup flour, baking powder, and salt; stir until smooth. Drop dough by rounded teaspoonfuls 2 inches apart onto prepared baking sheets. Bake at 350 degrees for 15 minutes. Remove cookiesfrom pan; let cool on wire racks. Yield: 3 dozen (serving size: 1cookie).