Position rack in center of oven and preheat the oven to 400 degrees F.

Melt the butter in a large nonstick skillet over medium heat. Add onion, garlic, red bell pepper, jalapeno, and corn. Cook, stirring occasionally, for 10 minutes, until the vegetables are softened. Add 1/4 teaspoon of the salt to the vegetables. Remove from the heat and cool.

Pour 2 tablespoons of the oil or bacon grease into a 9-inch cast-iron skillet. Place the skillet in the preheated oven for 10 minutes.

In a medium mixing bowl, stir together the flour, cornmeal, baking powder, sugar, and the remaining 1 teaspoon of salt.

Add the cheese, cooled vegetables, eggs, buttermilk, and remaining 2 tablespoons of oil or bacon grease to the flour mixture. Whisk until just combined. Do not overmix.

Using oven mitts or pot holders, carefully remove the hot skillet from the oven. Carefully pour the cornmeal batter into the hot skillet, making sure that the hot grease does not splash out.

Using oven mitts or pot holders, return the skillet to the oven. Bake for 25 to 30 minutes, until golden brown and cooked through.

Using oven mitts or pot holders, remove the cornbread from the oven and allow to sit for a few minutes before cutting into wedges and serving.