Place butter in an 8x8 inch casserole dish and place it in the oven. Preheat the oven to 450 degrees F.
In a large bowl add the flour, baking powder, and granulated sugar. Whisk together to mix thoroughly.
Pour the buttermilk into the flour mixture and use a fork to stir everything together until all ingredients are combined. Do not overwork! This will be a very moist, rough dough.
Once the oven is preheated, carefully remove the hot dish and add the dough. Use your fingers to spread it over the entire bottom of the dish.
Use a knife to cut lines in the dough, segmenting it into 9 equal pieces.
Bake for 25-30 minutes.
Remove the hot dish from the oven and serve the biscuits hot.