Preheat your oven to 450°F.
Pour melted butter into an 8x8-inch baking dish, ensuring it evenly coats the bottom.
In a mixing bowl, combine baking mix, sugar, baking powder, and salt.
Stir in the buttermilk until just combined. Do not overmix.
Pour the biscuit batter over the melted butter in the dish and gently spread it evenly.
Use a knife to score the unbaked dough into 9 squares (3x3 grid).
Bake for 20-25 minutes or until the top is golden brown and the center is set.
Let cool slightly before serving. Enjoy warm!