Step 1: Preheat your oven to 400°F (200°C). Place a 9-inch cast-iron skillet (or an 8x8 inch baking dish) in the oven with 2 tablespoons of butter inside to melt as the oven preheats.
Step 2: In a large mixing bowl, whisk together the dry ingredients: cornmeal, all-purpose flour, granulated sugar, baking powder, baking soda, and salt.
Step 3: In a separate medium bowl, whisk together the wet ingredients: buttermilk and eggs until well combined.
Step 4: Once the butter in the skillet is melted and sizzling, carefully remove the hot skillet from the oven. Swirl the butter around to coat the bottom and sides evenly. Pour 1 tablespoon of the melted butter into the wet ingredients mixture, whisking quickly to combine.
Step 5: Pour the remaining hot butter from the skillet back into the skillet. Immediately add the wet ingredients to the dry ingredients, mixing with a spoon or spatula until *just* combined. Do not overmix; a few lumps are fine.
Step 6: Quickly pour the cornbread batter into the hot, buttered cast-iron skillet. Spread it evenly.
Step 7: Bake for 20-25 minutes, or until the top is golden brown and a wooden skewer inserted into the center comes out clean.
Step 8: Once baked, remove the skillet from the oven. Let the cornbread cool in the skillet for about 5-10 minutes before inverting it onto a wire rack to cool completely, or serve warm directly from the skillet.