Preheat the oven to 450°F.
Add flour, baking powder, sugar, and salt to a medium bowl. Use a whisk to sift ingredients.
Pour in the buttermilk and stir until mostly combined, being careful not to overwork the batter.
Pour the melted butter into an 8x8-inch baking dish*. Place the dough on top of the butter and use a spatula (or your hands) to evenly spread the dough out to the edges of the pan.
Cut the unbaked dough into 9 squares (3x3 pattern). Bake for 28 minutes, or until the tops are golden brown.
Allow the butter to be absorbed into the biscuits before cutting and serving.