Preheat your oven to 375°F (190°C).

In a large skillet over medium heat, add 1 pound of ground beef along with diced onions, salt, and pepper. Cook for 5-7 minutes until fully cooked.

Stir in 1 can of cream of mushroom soup and ½ cup of sour cream, mixing until well-combined. Heat for 3-5 minutes.

Grease your 9x13 inch baking dish and spread the beef and mushroom mixture evenly across the bottom.

Sprinkle 1 cup of shredded cheddar cheese over the beef layer.

Layer the frozen tater tots in a single layer on top of the cheese.

Bake the casserole for 25-30 minutes until the tater tots are golden and crispy.

Remove from oven and add remaining cheddar cheese on top, returning to oven for an additional 5 minutes.

Allow the casserole to cool for 5 minutes before serving.