Preheat oven to 400F (200C). Grease a 9-inch cast iron skillet or baking dish.
In a large bowl, whisk together cornmeal, flour, sugar, baking powder, baking soda, and salt.
In a separate bowl, whisk together buttermilk, milk, and egg.
Pour the wet ingredients into the dry ingredients and mix until just combined. Do not overmix.
Stir in the melted butter until evenly distributed.
Pour the batter into the prepared skillet or baking dish.
Bake for 20-25 minutes, or until golden brown and a toothpick inserted into the center comes out clean.
Serve warm.
Notes
For extra richness, use buttermilk. Serve warm with butter and honey, or as a side to chili or stews. Can be made in a cast iron skillet for an even crispier crust.