1. Preheat the oven to 350°F.

2. Heat the vegetable oil in a large pot over medium heat. Add the diced onion and cook for about 3 minutes, stirring occasionally, until softened.

3. Add the ground beef, salt, cumin, and chili powder. Cook while breaking the meat into small pieces until browned and no longer pink, about 5 to 6 minutes.

4. Stir in the black beans with their liquid, frozen corn, and drained diced tomatoes with green chiles. Let the mixture simmer while you prepare the cornbread topping.

5. In a medium bowl, whisk together the cornmeal, flour, salt, baking powder, and baking soda.

6. Add the buttermilk and vegetable oil to the dry ingredients. Stir until smooth, then fold in the shredded cheddar cheese.

7. Check the chili mixture. It should be thick and moist without too much liquid. Simmer a few extra minutes if needed to reduce excess moisture. Taste and adjust seasoning if desired.

8. Remove the chili from the heat and stir in the 2 cups of shredded cheddar cheese.

9. Spread the chili mixture evenly into a 9 x 13-inch baking dish. Layer the cheese slices across the top.

10. Spoon the cornbread batter over the cheese layer and gently spread it evenly.

11. Bake for 30 to 35 minutes, or until the cornbread is golden brown and a toothpick inserted into the topping comes out clean.

12. Let cool slightly before serving. Add your favorite toppings if desired.