Set oven to 425. Heat a 9-inch cast-iron skillet over medium-high heat.
In a large mixing bowl, combine first 5 ingredients. In a separate bowl, combine butter, eggs, and buttermilk. Pour wet ingredients over the dry ingredients and mix until all ingredients are moistened (batter will still be lumpy).
Drop bacon grease into heated skillet (or cook bacon). Once grease is melted down, pour batter into the skillet. Place immediately into the oven.
Bake for 25 minutes or until a toothpick inserted into the middle comes out clean. Let cool in the skillet for 10 minutes.
Slice into wedges, top with butter, and enjoy!
Recipe by This Cookin' Dad at https://thiscookindad.com/2015/03/cast-iron-cornbread/