1 1/2 cups powdered sugar 1 teaspoon baking soda 1 teaspoon cream of tartar 1/4 teaspoon salt 1 cup butter 1 large egg 1 teaspoon vanilla extract 2-1/4 cups all-purpose flour
Preheat oven to 350°F.
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.