Preheat oven to 425°F (220°C). Whisk flour, baking powder, baking soda, salt, and sugar. Work cold butter into the flour with a pastry cutter or fingertips until coarse crumbs form.

Stir in buttermilk with a fork until a shaggy dough comes together. Add another tablespoon if it seems dry.

Turn dough onto a floured surface, pat to 1 inch thick, fold, and repeat 3 times. Pat to 3/4 inch thickness, cut 8 rounds without twisting the cutter, and place on a parchment-lined sheet.

Bake 12 to 15 minutes until deep golden on top and firm when tapped.

Brush hot biscuits with melted butter and cool on the sheet for 5 minutes before serving warm.