Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
In a large skillet, cook the ground beef and diced onion over medium heat until browned. Drain any excess fat.
Stir in the soup, ketchup, mustard, half of the crumbled bacon, and 1 cup of the shredded cheddar cheese. Season with salt and pepper.
Spread the beef mixture evenly into the prepared baking dish.
Arrange the frozen tater tots in a single layer on top.
Sprinkle with the remaining cheese and bacon.
Bake uncovered for 35–40 minutes, or until the tater tots are golden and crispy, and the cheese is melted.
Let it rest for 5 minutes before serving. Top with your favorite garnishes and enjoy!