Preheat the oven to 400 degrees F. Brown the ground beef in a large skillet over medium heat. Drain any excess fat.
Stir the taco seasoning, black beans, corn, and salsa into the skillet. Let the mixture simmer for 5 minutes until heated through.
Spread the beef mixture evenly into an 8x8 inch baking dish.
In a mixing bowl, combine the cornbread mix, egg, and milk until just blended. Pour this batter over the beef layer and spread it gently to cover.
Sprinkle the shredded cheddar cheese evenly across the top.
Bake for 20 to 25 minutes until the cornbread is golden and a toothpick inserted in the center comes out clean.