Preheat the oven to 400°F. Place 9 inch cast iron skillet in the oven to heat.
Whisk the cornmeal, flour, sugar, baking powder, baking soda, and salt in a bowl.
Whisk the buttermilk, eggs, and butter in a separate bowl.
Pour the wet ingredients into the dry ingredients and stir until just combined. Avoid overmixing. Spread the batter into the cast iron pan and bake for 20-25 minutes, until the top is golden brown and a toothpick inserted into the center comes out clean.