Preheat oven to 220°C. Cook ground beef over medium heat for 6–8 minutes until browned, breaking it apart, then drain fat. Add bacon, onions, ketchup, mayonnaise, mustard, salt, and pepper, mix well, then remove from heat.
Hollow out each tater tot with a small knife or spoon to form cone shapes, letting them soften slightly if too firm.
Fill each cone with the beef mixture, pressing gently to hold shape without cracking.
Sprinkle cheddar cheese evenly over the filled cones.
Bake on a tray at 220°C for 15–18 minutes until golden, crispy, and cheese is melted and bubbly.