Preheat your oven to 375°F (190°C).
In a large skillet, brown the ground beef over medium heat until fully cooked, about 6-8 minutes.
Add the diced onion to the skillet and sauté for 2-3 minutes until softened.
Stir in the ketchup, Worcestershire sauce, mustard, garlic powder, and season with salt and pepper.
Remove the skillet from heat and spread the beef mixture into a greased 9x13 inch baking dish.
Top the beef mixture with a layer of Tater Tots, arranging them in a single layer.
Sprinkle the shredded cheddar cheese over the Tater Tots evenly.
Bake in the preheated oven for 30-35 minutes until the tater tots are golden brown and the cheese is bubbly.
Allow the casserole to cool slightly before serving for 5-10 minutes.