Preheat the oven to 425°F (220°C). Pour the 1/2 cup melted butter into a 9x13-inch baking pan, tilting to coat the bottom evenly.

In a large mixing bowl, whisk together the flour, baking powder, and salt until well combined.

Add the cold, cubed butter to the dry ingredients and cut it in with a pastry cutter or fork until the mixture resembles coarse crumbs with pea-sized pieces of butter visible.

Pour the cold buttermilk into the bowl and gently fold with a spatula just until no dry flour remains. The dough will be shaggy.

Lightly flour a work surface and turn the dough out. Knead gently 6–8 times until it comes together.

Roll the dough to about 1/2-inch thickness using a floured rolling pin.

Cut the dough into 12 biscuits with a 2-inch cutter or sharp knife, pressing straight down without twisting.

Arrange the cut biscuits in three rows of four in the buttered pan; they should sit in, but not be submerged by, the butter.

Bake for 20–25 minutes, until the tops are deep golden brown and the butter is bubbling around the edges.

Remove from the oven and let rest 2–3 minutes before serving warm, spooning any extra melted butter over the tops if desired.