Heat oven to 375°F. Combine butter, powdered sugar and 1/2 cup sugar in large bowl. Beat at medium speed, scraping bowl often, until creamy. Add egg and vanilla; continue beating until well mixed. Reduce speed to low; add flour, cream of tartar and baking soda. Beat until dough forms a ball.
Shape dough into 1-inch balls. Place 2 inches apart onto Reynolds Parchment paper on cookie sheets. Flatten to about 1 1/2 inches with bottom of glass dipped in sugar; sprinkle with decorator sugars, if desired. Bake for 7 to 9 minutes or until edges are lightly browned. Let stand 1 minute on cookie sheet; remove to cooling rack.