**Preheat the Oven:** Preheat your oven to 375°F (190°C) and lightly grease a loaf pan or baking dish.
**Prepare the Meatloaf Mixture:** In a large mixing bowl, combine ground beef, ground pork or turkey, breadcrumbs, Parmesan cheese, soup mix, milk, egg, pepper, and garlic powder. Mix until just combined.
**Shape and Bake:** Shape the mixture into a loaf and place it in the prepared pan. Bake for 40–45 minutes.
**Prepare the Onion Glaze:** While the meatloaf bakes, melt butter in a skillet over medium heat. Add onions and sugar, stirring until caramelized (about 10 minutes). Sprinkle flour over the onions and cook for 1 minute. Gradually add beef broth and Worcestershire sauce, whisking until thickened.
**Top and Finish:** Remove the meatloaf from the oven. Spread the onion glaze over the top and sprinkle with cheese. Return to the oven and bake for an additional 10–15 minutes, or until the cheese is melted and bubbly.
**Rest and Serve:** Let the meatloaf rest for 10 minutes before slicing and serving.