Place a 9- or 10-inch cast iron skillet in the oven and preheat the oven to 400ºF.

Combine the cornmeal, flour, baking powder, baking soda, and salt in a mixing bowl. Whisk to combine.

In a separate bowl, whisk together the buttermilk, sugar, eggs, and 6 tablespoons melted butter. Add the wet ingredients to the dry and stir to combine.

Carefully remove the skillet from the oven, add 2 tablespoons butter to the pan, and swirl to coat. Pour in the batter, smooth the top, and bake for 30 minutes or until golden brown and a toothpick inserted into the center comes out clean. Let cool in the pan for 10 minutes.