Preheat the oven to 400°F (200°C) and lightly grease a 9x13 inch baking dish.
In a large skillet over medium-high heat, brown the ground beef and diced onion until the beef is fully cooked and onions are translucent. Drain excess fat.
Stir in the taco seasoning, corn, black beans, and enchilada sauce. Simmer for 5 minutes over low heat.
Transfer the beef mixture into the prepared baking dish and spread it into an even layer.
In a medium mixing bowl, combine the cornbread mix, milk, egg, and 0.5 cup of the shredded cheddar cheese. Stir until just combined; do not overmix.
Spread the cornbread batter evenly over the top of the beef mixture.
Bake in the preheated oven for 20 to 25 minutes, or until the cornbread topping is golden brown and a toothpick inserted into the center of the crust comes out clean.
Sprinkle the remaining 1 cup of cheddar cheese over the crust and bake for an additional 2 to 3 minutes until the cheese is melted and bubbling.
Allow the pie to rest for 5 minutes before slicing and serving.