In a large ovenproof skillet or Dutch oven set over medium heat, cook the ground beef, breaking up the meat with a wooden spoon, until browned through, 3 to 5 minutes. Drain the fat from the meat. Add the onion, garlic, jalapeno, pinto beans, tomato sauce, and tomato and remove the pan from the heat. Top with the cheese.
In a medium bowl, combine the cornmeal, flour, egg, and buttermilk. Pour the mixture on top of the meat mixture.
Bake until the cornbread topping is lightly browned, 15 to 20 minutes. Serve hot.