Preheat oven to 375°F.
Lightly spray the bottom of a 9x13 pan with cooking spray. Place the tater tots in the dish and pre-bake for 8 minutes. Remove from the oven and transfer to a bowl.
Turn the oven up to 425°F.
In a large skillet cook your onions and ground beef until beef is no longer pink and onions are tender.
Pour in the Rotel tomatoes, garlic powder, onion powder, and black pepper. Cook until the liquid has reduced, about 8 minutes.
Remove from the heat and add sour cream, cream of mushroom soup, drained corn, ½ cup of cheese. Stir until the cheese is melted.
Pour the mixture into the bottom of the baking dish and spread evenly.
Sprinkle ½ cup of cheese over the top of the casserole.
Layer the tater tots on top,pressing them down into the mixture.
Sprinkle the remaining ½ cup of cheese over the top of the tater tots.
Sprinkle the chopped chives over the cheese.
Cover and bake at 425°F for 20 minutes. Uncover and bake for an additional 5 to 10 minutes.
Remove from oven and serve.