How to Make It
Preheat oven to 425°F. Heat oil in a 10-inch cast-iron skillet over high. Add beef and onion; cook, stirring often, until beef is browned and crumbly, 5 to 7 minutes. Stir in tomatoes, beans, chili sauce, 1/4 cup water, chili powder, salt, and 1 finely chopped and seeded jalapeño. Bring to a boil, and remove from heat. Sprinkle top with 1 cup of the cheese.
Whisk together corn muffin mix, milk, egg, and remaining 1/2 cup cheese. Pour batter over hot filling in skillet, spreading batter to edges of skillet. Thinly slice remaining jalapeño; sprinkle slices over top of batter.
Bake in preheated oven until cornbread is golden brown, 18 to 22 minutes.