Heat oven to 375 degrees. Combine butter, powdered sugar and 1/2 C. sugar in large bowl. Beat at medium speed, scraping bowl often, until creamy. Add egg and vanilla; continue baking 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 ungreased cookie sheets.

Flatten to about 1 1/2 inches with bottom of glass dipped in sugar; sprinkle with decorator sugars, if desired. Bake 7-9 minutes or until edges are lightly browned. Let stand 1 minute; remove from cookie sheets.

Frost with cream cheese frosting and sprinkle decorator sugar on top, if desired.