Preheat oven to 400 degrees F. Place a 10-inch cast iron skillet in the oven and heat for at least 30 minutes. Meanwhile make the batter.
Whisk together the flour, cornmeal, sugar, baking powder, and salt in a large bowl. In a medium bowl, whisk together the milk, eggs, and melted butter.
Make a well in the center of the dry ingredients and pour the wet ingredients into the well. Use a fork or spatula to stir until evenly combined.
Remove the skillet from the oven. *****Warning***** Make sure you are using an oven mitt to do this. The skillet is very hot. Add the bacon fat to the skillet, and swirl to coat. Pour the batter into the skillet and, using a spatula, spread the batter evenly across the pan.
Bake for 25 to 30 minutes, until lightly golden and firm and springy to the touch. ****Melt an additional 2 tablespoons of butter over the top of the cornbread when it comes out of the oven.****