French Butter Cream Cookies

Preheat oven to 350 °F (175°C). Combine sugar, butter, egg, vanilla, baking soda, cream of tartar and salt in a medium mixing bowl. Beat until light and creamy. Add flour gradually until well blended. Wrap dough in plastic and chill for an hour. Shape dough into ¾-inch balls and place 2 inches apart on a baking sheet. Flatten with a fork. If desired, sprinkle with colored sugar. Bake for 5 to 8 minutes until set, but not browned. Cool on cookie sheet for 10 minutes before removing to a wire rack.