Preheat the oven to 425 degrees F (220 degrees C). Line a baking sheet with parchment paper.

Sift flour, cream of tartar, baking soda, and salt into a large bowl.

Rub in butter until the mixture resembles fine breadcrumbs. Stir in sugar and enough milk to mix to a soft dough.

Turn dough onto a floured surface, fold over 2 or 3 times, then roll out to a 3/4-inch thickness. Cut into 2-inch rounds and place on the prepared baking sheet; brush tops with milk to glaze.

Bake in the preheated oven until scones are risen and golden on top, about 10 minutes. Cool scones on a wire rack.