Preheat oven to 425°F (218°C). Whisk flour, baking powder, sugar, and salt. Cut in cold butter until the mixture resembles coarse crumbs. Add cold buttermilk and stir until just combined.
Turn dough onto a floured surface, pat into a rectangle, and fold over itself 3–4 times. Pat to 1-inch thickness and cut using a biscuit cutter. Place on parchment-lined baking sheet with edges just touching.
Bake for 15 minutes until golden brown. Cool slightly.