Preheat your oven to 400°F (205°C). Place a 9-inch cast-iron skillet in the oven to heat up while you prepare the batter.
In a large mixing bowl, whisk together the cornmeal, flour, sugar (if using), baking powder, baking soda, and salt.
In a separate medium-sized bowl, combine the buttermilk, melted and cooled butter, and beaten eggs.
Slowly pour the wet ingredients into the dry ingredients, and mix gently until just combined. Be careful not to overmix, as this can result in a dense cornbread.
Carefully remove the hot cast-iron skillet from the oven and add 2 tablespoons of butter, swirling it around to evenly coat the bottom and sides of the skillet. The extra butter will help create a beautiful crispy crust on your cornbread.
Pour the cornbread batter into the greased skillet, spreading it evenly with the spatula.
Bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean, and the top is golden brown.
Allow the cornbread to cool for a few minutes before cutting it into wedges or squares. Serve warm with butter, honey, or your favorite accompaniment.