Preheat oven to 400 degrees F. Place a 9-inch cast iron skillet in the oven to get it really hot.
Combine the dry ingredients in bowl: flour, cornmeal, sugar, baking powder, baking soda, and salt. Set aside.
In a separate large bowl, whisk the buttermilk, milk, eggs, and 1/2 cup melted butter until well-combined.
Add the dry ingredients to the wet ingredients. Mix until your batter is fully incorporated and smooth. Do not overmix.
Remove hot skillet from oven. Coat the hot skillet with 1 tablespoon of butter. Immediately, add the batter and bake for about 20-25 minutes, or until a toothpick or cake tester inserted in the middle comes out clean and the top is golden brown.
Let rest for 10-15 minutes before serving. Enjoy!