Preheat oven to 450°F (232°C).

Spread bacon grease in a 10-inch cast-iron skillet.

Place the skillet in the preheating oven to heat the grease.

In a bowl, whisk together the egg and buttermilk.

Incorporate baking powder, baking soda, and salt into the wet mixture.

Stir until well combined.

Gradually add cornmeal until the batter resembles pancake batter consistency.

Carefully remove the hot skillet from the oven when the bacon grease is nearly smoking.

Pour the batter into the hot skillet all at once.

Return the skillet to the oven.

Bake for approximately 15 minutes, or until the top is lightly golden brown.

Remove from the oven and invert onto a plate.

Serve immediately with butter.