In a bowl, cream butter, sugar and egg until well blended. Add lemon juice and peel. Combine flour, baking soda, cream of tartar and salt; stir into creamed mixture. Cover and refrigerate the dough for at least 1 hour.
Roll into 1-in. balls or using a small cookie scoop. Place on ungreased baking sheet. Bake at 350° for 9 minutes or until bottoms are lightly browned (cookies will not brown on top).
Remove immediately to wire racks; cool for 5 minutes, then roll in confectioners' sugar. Yield: about 3 dozen