Preheat the oven to 375°F.
Chop the onion and tomato.
In a large skillet, cook the ground beef and onion, breaking the meat up as it cooks, until no longer pink. Add the minced garlic and cook for 1–2 more minutes.
Drain any grease. Stir in the corn, black beans, enchilada sauce, Rotel, and taco seasoning. Simmer on low for 5 minutes.
Pour the mixture into a greased 9x13 inch casserole dish and spread evenly. Top with a single layer of tater tots.
Bake for 35 minutes.
Remove from the oven, sprinkle with cheese, and bake for another 8–10 minutes until the cheese is melted.
Top with diced tomatoes, black olives, and green onions before serving.