Preheat oven to 400°F (200°C). Place a cast-iron skillet in the oven while it preheats.
In a large bowl, whisk together cornmeal, flour, sugar (if using), baking powder, baking soda, and salt.
In a separate bowl, whisk together buttermilk, egg, and melted butter.
Pour wet ingredients into dry ingredients and stir until just combined.
Carefully remove the hot skillet from the oven and pour batter into skillet.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Let cool slightly before slicing and serving.
Notes
For a sweeter cornbread, add more sugar. For a savory cornbread, omit the sugar or add spices like chili powder or cumin.Nutrition: (Note: nutrition information is an estimate and will vary based on ingredients)