Preheat your oven to 350°F (175°C) and spray a muffin tin with nonstick cooking spray.

In a large mixing bowl, combine ground beef, white onion, eggs, breadcrumbs, Worcestershire sauce, pepper, seasoning salt, and garlic powder. Mix gently.

In a small bowl, mix together ketchup, brown sugar, and mustard for the topping.

Scoop the meat mixture into each muffin cup, pressing down slightly.

Spoon the ketchup topping over each filled muffin cup.

Bake in the preheated oven for about 30 minutes until golden and internal temperature reaches 160°F (71°C).

Remove from the oven, let cool for 5 minutes, then serve warm.