Preheat the oven to 450°F.
Coat the sides and bottom of 10-inch cast-iron skillet with the bacon grease, vegetable oil or shortening. Place skillet in the oven to heat.
In a bowl, combine the cornmeal, baking powder, baking soda, salt and pepper and mix well. In a small bowl combine the buttermilk, egg, melted butter, and jalapenos. Add to the dry ingredients and stir just to combine. Remove the hot skillet from the oven, carefully swirl to evenly distribute hot grease, and quickly pour the cornmeal batter into the skillet.
Bake for 25 to 30 minutes, or until firm and golden brown on top. Let sit for 5 minutes, then turn out onto a cutting board. Cut into wedges and serve hot with butter on the side.