In a large bowl, mix together ground meat, diced onion, and salsa. Then, season with taco seasoning, salt, and pepper.
Place mixture into a large casserole dish. Then, pour on a can of black beans and corn.
Bake at 375ºF for 45 minutes. Use a large spoon to remove and grease that has come to the top. Sprinkle on cheese, place back in the oven for about 30 more minutes. Remove any more grease that has come to the top.
Serve with hard shell tacos, Greek yogurt or sour cream, and avocado.