Preheat oven to 375°F (190°C). Grease a baking dish.
Cook ground beef in a skillet until browned. Add onion and garlic; cook until soft. Season with salt, pepper, paprika, and Italian seasoning. Stir in ketchup and mustard if using. Drain excess fat.
In a saucepan, melt butter. Whisk in flour and cook 1–2 minutes. Slowly add milk, whisking until thickened.
Stir in cheddar, mozzarella, garlic powder, and onion powder until smooth.
Spread beef mixture evenly in baking dish.
Pour cheese sauce over beef layer.
Arrange tater tots on top in a single layer.
Bake uncovered for 40–45 minutes until tater tots are crispy and golden.
Sprinkle cheddar cheese on top and bake another 5–10 minutes until melted.
Let rest for 10 minutes before serving.