|Preheat oven to 400°F/205°C. Mix flour, cream of tartar, baking soda, and salt in medium bowl; set aside. In large bowl, beat sugar, butter, shortening and eggs with electric mixer until well-blended and smooth. Stir in flour mixture.
Refrigerate dough, if needed, until firm enough to shape.
Shape level tablespoonfuls of dough into 1-1/2 inch/35-mm balls. Roll in mixture of remaining sugar and cinnamon. Place 2 inches/5 cm apart on ungreased cookie sheets. Bake for 8 to 10 minutes or until lightly browned and tops are crinkled. Remove to wire rack to cool.
Makes 48 cookies.