Preheat oven to 425°F. Line a baking sheet with parchment paper.

In a large bowl, whisk together flour, baking powder, baking soda, sugar, and salt.

Cut in butter using a pastry cutter until the mixture resembles coarse crumbs with small butter pieces visible.

Pour in buttermilk and stir gently until just combined.

Turn dough out onto a floured surface and gently knead 4–5 times to bring it together.

Pat into a rectangle, fold in half, rotate, and repeat once to create layers.

Roll to 1-inch thickness and cut into 9 even squares using a sharp knife.

Arrange biscuits on prepared pan, brush tops with buttermilk.

Bake 15–18 minutes, or until golden brown.

Brush hot biscuits with melted butter before serving.