Preheat your oven to 400°F (200°C) and grease a 9x13 inch baking dish with cooking spray or butter.
In a large mixing bowl, combine the cornmeal muffin mix, eggs, and milk. Stir until combined and smooth.
Add the black beans, corn, salsa, diced bell peppers, diced red onion, ground cumin, chili powder, salt, and black pepper to the cornmeal mixture. Fold everything together gently until well combined.
Pour the mixture into the prepared baking dish evenly.
Sprinkle the shredded cheddar cheese over the top of the casserole.
Bake in the preheated oven for 25-30 minutes or until golden brown on top and a toothpick inserted into the center comes out clean.
Remove from the oven and let it cool slightly before slicing into squares.
Serve warm garnished with fresh cilantro if desired.
Notes
Serve warm garnished with fresh cilantro if desired.