½cupunsalted butterchilled, plus melted butter for brushing
Preheat the oven to 450 degrees F.
Sift flour, baking powder, sugar, salt and cream of tartar together into a large bowl.
Cut in cold butter until the mixture is the consistency of coarse oatmeal.
Make a well in the center of the mixture and pour in buttermilk. Stir with a wooden spoon until dough begins to come together. Press dough together, but use your hands as little as possible, since it will warm up the butter in the dough.
On a lightly floured surface, roll out dough to about ¾ inch thick. Use a cookie cutter to cut 2-inch round biscuits, then place on an ungreased baking sheet.
Bake for 10 minutes, or until golden brown. Brush with melted butter as soon as biscuits come out of the oven. Serve warm.
Make Ahead: Cut the biscuits from the dough and transfer to a parchment-lined baking sheet. Cover it lightly with plastic wrap and put the baking sheet in the freezer until biscuits are frozen solid, then transfer to a a large resealable plastic freezer bag and freeze for up to 3 months. Thaw at room temperature, and once thawed, bake in the oven for 10 minutes. Fully baked biscuits can be stored in an airtight container on the counter for 1–2 days, or for 1 week in the refrigerator. Cutting in Butter: Use a cheese grater to grate the cold butter into the dry ingredients, then cut it in with a pastry blender.