Prepare the cornbread mix according to package. Pour into 9x13 baking dish and bake according to package. Let cool and set aside. Leave oven on, adjust temperature to 350ºF.
Meanwhile, in a large pan brown your ground chuck. Drain fat. Add in chopped onion. Cook until browned.
Add in corn, black beans, green chiles, cheese, and taco seasoning. Combine well. Pour mixture over corn bread.
In a small bowl, combine salsa and sour cream. Spread mixture on top of casserole.
Arrange tater tots as final layer. Bake at 350ºF for 20 minutes or until tater tots are browned.