Preheat your oven to 400°F (200°C).
In a large mixing bowl, combine the black beans, corn, diced tomatoes with green chilies, and ½ cup of shredded cheese. Mix them until well combined.
In a separate bowl, prepare the cornbread mix according to the package instructions. Add the milk, egg, chili powder, ground cumin, salt, and black pepper, and mix until just combined.
Pour the mixed corn and bean mixture into the bottom of the baking dish, spreading it evenly.
Carefully pour the cornbread batter over the top of the bean and corn mixture, spreading it gently to cover it fully.
Sprinkle the remaining cheese on top of the cornbread batter.
Place the baking dish in the preheated oven and bake for 30 minutes, or until the cornbread is golden brown and a toothpick inserted in the center comes out clean.
Remove from the oven and let it cool for a few minutes before slicing. Garnish with fresh cilantro or green onions if desired.