Preheat your oven to 400°F (200°C).
In a large skillet over medium-high heat, cook the ground beef and diced onion until the beef is browned and the onions are translucent. Drain excess grease.
Remove the skillet from heat and stir in the cream of mushroom soup, sour cream, half of the shredded cheddar cheese, and any optional seasonings like garlic powder or paprika.
Transfer the beef mixture into a 9×13 inch casserole dish and spread it into an even layer.
Arrange the frozen tater tots in a single layer over the top of the beef mixture.
Bake for 25 minutes, then remove from the oven and sprinkle the remaining cheese over the tots.
Return to the oven for an additional 10 minutes, or until the tots are golden brown and crispy and the cheese is bubbly.