Heat the oven to 375°F and position the rack in the center. Generously grease an 8x8-inch square baking dish or a 2-quart casserole dish with butter, ensuring all sides are lightly coated to prevent sticking.

In a large mixing bowl, combine the fresh blueberries, sugar, and flour. Gently toss until the berries are evenly coated, ensuring no pockets of dry flour remain. Pour the coated blueberries into the prepared baking dish, spreading them evenly. Scatter the small pieces of butter evenly over the top, allowing them to melt into the fruit as it bakes.

In a separate medium-sized bowl, whisk together the flour, 6 tablespoons of sugar, baking powder, baking soda, salt, and grated lemon zest. Add the cold butter chunks to the mixture. Using your fingertips, a pastry cutter, or a fork, work the butter into the dry ingredients until the mixture resembles coarse crumbs with small, pea-sized butter clumps throughout.

Pour the buttermilk into the bowl and gently stir until the dough just comes together. The mixture should be slightly lumpy but combined avoid overworking the dough to maintain its light and tender texture.

Using a large spoon, drop 8–10 generous dollops of the biscuit dough over the blueberry mixture, leaving small spaces for the berries to peek through. Sprinkle the remaining tablespoon of sugar evenly across the surface of the biscuit topping for a lightly sweetened, golden finish.

Place the dish in the preheated oven and bake for approximately 35 minutes, or until the fruit filling is bubbling at the edges and the biscuit topping is golden brown.

If the top is golden but the center still appears undercooked, loosely cover the cobbler with foil and continue baking for an additional 10 minutes. If the topping hasn’t browned, leave it uncovered and bake for 10 minutes more. Remove any foil, if used, and allow the cobbler to rest at room temperature for 15–20 minutes before serving.

Spoon the warm cobbler into bowls and serve it with a generous scoop of vanilla ice cream or a dollop of whipped cream for an indulgent, classic pairing.