In a mixing bowl, whisk together the flour, sugar, baking powder, and salt.
Slowly stir in the buttermilk until just combined. Do not overmix.
Pour the melted butter into an 8x8-inch baking dish.
Spread the biscuit dough evenly over the butter.
Cut the unbaked dough into 9 squares for easy separation after baking.
Preheat your air fryer to 320°F (160°C).
Place the baking dish in the air fryer and cook for 20-25 minutes until golden brown.
Let cool slightly before serving.