Preheat the oven to 350°F.
In a large skillet over medium heat, brown the ground beef and diced onion until the beef is cooked through and the onion is translucent, about 5-7 minutes. Drain any excess fat.
Stir in the black beans, corn, cream of mushroom soup, garlic powder, chili powder, salt, and pepper. Mix well until all ingredients are combined and heated through, about 3-5 minutes.
Spread the beef mixture evenly in a greased 9x13-inch baking dish.
Layer the frozen tater tots on top of the beef mixture in a single layer.
Bake in the preheated oven for 30-35 minutes, or until the tater tots are golden brown and crispy.
Remove from the oven and sprinkle the shredded cheddar cheese on top. Return to the oven for an additional 5 minutes, or until the cheese is melted.
Let the casserole cool for a few minutes before serving. Garnish with fresh cilantro or green onions if desired.