Combine flour, cocoa powder, baking soda, cream of tartar and salt in medium bowl; set aside.
Beat Country Crock® Spread, granulated sugar and 1/2 cup confectioners sugar in large bowl with electric mixer until light and fluffy. Beat in egg and vanilla until blended. Gradually beat in flour mixture just until blended.
Shape dough into 1-inch balls, then arrange on ungreased baking sheets, 2 inches apart.
Bake 10 minutes or until bottom of cookies are slightly golden. Cool 2 minutes on wire rack; remove cookies from sheets and cool completely.
If desired, place an additional 1 teaspoon confectioners sugar in small fine-mesh sieve and sprinkle lightly over cookies.
See nutritional information for saturated fat content.