Preheat Oven: Set oven to 450°F.
Prepare Butter: Melt butter in a cast iron skillet or 8x8-inch baking dish in the preheated oven. Watch closely to avoid burning.
Mix Dry Ingredients: In a large bowl, whisk together flour, baking powder, sugar, and salt.
Add Buttermilk: Gradually stir in buttermilk until just combined. The dough will be lumpy.
Combine with Butter: Pour biscuit batter over the melted butter in the skillet or dish.
Bake: Bake for 25-30 minutes until golden brown and set in the middle.
Cool: Let the biscuits sit in the pan for 15 minutes to absorb the butter.