In a bowl, combine flour cornmeal, sugar, baking powder, cream of tartar and salt. Cut in butter until mixture resembles coarse crumbs. Combine egg and milk; stir into flour mixture just until moistened. Let stand 5 minutes.
Turn onto a floured surface; knead for about 1 minute. Pat or roll out to 3/4-in, thickness; cut with a 3-in. biscuit cutter. Place on a greased baking sheet. Bake at 450° for 10-12 minutes.