PREHEAT oven to 450°F. Mix flour, baking powder, salt, cream of tartar and baking soda in large bowl until well blended. Cut in shortening until mixture resembles coarse crumbs. Add buttermilk; stir with fork until mixture forms a soft dough.
PLACE on lightly floured surface; knead 20 times or until smooth. Pat or roll out dough to 1/2-inch-thickness. Cut into circles with floured 2-inch cookie cutter. Place on ungreased baking sheet. Brush with half of the butter.
BAKE 12 minutes or until golden brown. Brush with remaining butter.