Preheat your oven to 425°F. Put the bacon grease in your cast iron skillet or baking dish and put that in the oven while it's preheating.
Mix all the dry ingredients together well.
Mix the buttermilk and the eggs together until fully combined.
Combine the wet and dry ingredients.
Add the melted butter and continue mixing until the butter is fully incorporated.
Allow the mixture to rest for 10 mins before baking. This will also give your oven time to fully preheat.
Carefully pour the batter into the preheated skillet/baking dish, being careful not to splash any grease onto the oven (or yourself).
Reduce the heat to 375°F and cook until the top is lightly browned and a toothpick inserted into the center comes out dry. (About 30-40 mins)
Remove from the pan immediately and allow to cool for about 10 minutes before cutting and serving.