Prepare the Skillet: Preheat your oven to 400°F (204°C). Place your cast iron skillet in the oven to preheat as well.
Mix Dry Ingredients: In a mixing bowl, combine the flour, cornmeal, sugar, salt, and baking powder.
Combine Wet Ingredients: In another bowl, whisk together the egg, milk, and melted butter.
Combine Mixtures: Add the wet ingredients to the dry ingredients, stirring just until everything is moistened. If using, fold in the chopped jalapeño.
Bake the Cornbread: Carefully remove the hot skillet from the oven (don’t forget your gloves!) and add a bit of butter to coat. Pour the batter into the skillet, smoothing the top.
Bake: Return the skillet to the oven and bake for about 15-20 minutes, or until the top is golden and a toothpick inserted into the center comes out clean.
Cool and Serve: Allow the cornbread to cool for a few minutes before slicing. Serve warm with a pat of butter or alongside your favorite meal.