Preheat oven to 400°F (200°C).
In a large skillet over medium-high heat, brown the ground beef with diced onions until meat is no longer pink.
Add minced garlic and cook for an additional 60 seconds until fragrant.
Drain excess fat from the skillet.
Stir in the taco seasoning, enchilada sauce, black beans, and corn. Simmer for 5 minutes.
Transfer the beef mixture into a 9x13 inch baking dish and spread evenly.
Sprinkle 1 cup of the shredded cheese over the beef mixture.
Arrange the frozen tater tots in a single, even layer over the top.
Bake for 30 minutes or until the tater tots are golden brown and crispy.
Sprinkle the remaining 1 cup of cheese over the tots and bake for another 5 minutes until melted.
Let stand for 5 minutes before garnishing with cilantro and serving with sour cream.