Preheat oven to 375°F. Grease a 9x13-inch baking dish and set aside.
In a large skillet over medium-high heat, cook ground beef and chopped onion until meat is browned and onion is tender, about 8 minutes. Drain excess fat.
Stir in black beans, corn, diced tomatoes with green chilies, enchilada sauce, cumin, chili powder, and salt. Simmer for 5 minutes, then pour into prepared baking dish. Sprinkle 2 cups of shredded cheese over the meat mixture.
In a large bowl, whisk together cornmeal, flour, and baking powder. In a separate bowl, beat eggs, milk, and vegetable oil together.
Pour wet ingredients into dry ingredients and stir just until combined. Pour this batter evenly over the meat and cheese layer in the baking dish.
Bake uncovered for 35-40 minutes until topping is golden brown and set. Sprinkle remaining 1 cup cheese on top and bake for 5 more minutes until melted. Let stand for 10 minutes before serving.