In a medium bowl, stir together the flour, baking powder, sugar, salt, and cream of tartar. Cut in butter using a pastry cutter or a fork until it is the size of peas.
Make a well in the center of the mixture and measure the milk, cheese, and thyme into the bowl. Gently mix until a soft dough forms.
Roll or pat out the dough on a floured surface to 3/4 inch thick. Cut into circles and place on a baking sheet.
Bake for 10 minutes, or until the bottoms of the biscuits are brown.
