Preheat oven to 350 degrees F. Spray an 8x10-inch baking dish with nonstick cooking spray; set aside.

Add ground beef and onion to a large skillet over medium-high heat and cook for 6-8 minutes, breaking up meat, until meat is cooked through and onion is tender; drain excess grease.

Add enchilada sauce, black beans, Rotel, corn, taco seasoning, salt and pepper to the skillet. Mix to combine and let simmer for 5 minutes. Remove from heat and mix in 1⁄2 cup cheese then spread mixture in the bottom of prepared pan.

In a mixing bowl, combine corn muffin mix, egg and milk until well combined then spread over the ground beef mixture.