Preheat the oven to 450°F (232°C).
In a mixing bowl, whisk together flour, sugar, baking powder, and salt.
Pour in the buttermilk and stir until just combined. Avoid overmixing.
Pour the melted butter into an 8x8-inch baking dish, ensuring it coats the bottom evenly.
Transfer the dough into the dish, spreading it evenly without mixing it into the butter.
Using a knife, score the dough into 9 squares for easy cutting after baking.
Bake in the preheated oven for 20-25 minutes or until golden brown.
Cool slightly before serving.