Preheat the oven to 450°F (232°C).

In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt.

Gently fold in the cold buttermilk and fresh blueberries until a wet, shaggy dough forms.

Pour the melted butter into an 8x8-inch square baking dish, ensuring the bottom is completely covered.

Transfer the dough into the baking dish, spreading it gently with a spatula to the edges so it sits on top of the butter.

Using a knife or bench scraper, score the dough into a 3x3 grid to create 9 individual biscuits.

Bake for 25 to 30 minutes, or until the tops are golden brown and the butter has been fully absorbed by the biscuits.

Allow the biscuits to rest for 5 minutes before cutting through the scored lines and serving.