Preheat oven to 450. Mix flour, baking powder, cream of tartar, sugar, and salt in medium bowl. Cut in butter, until mixture resembles coarse crumbs. Stir in cheddar cheese. Add milk; stir until mixture forms soft dough. Place on lightly floured surface; knead 8-10 times or until smooth. Pat out dough into 6" square. Cut into 9 squares. Place on a greased baking sheet. Bake 10-12 minutes. Spread each warm biscuit with 2 1/2 t of cream cheese or butter.