Preheat oven to 350°F. Grease a 9x13 inch baking dish or casserole dish.
In a large bowl, combine ground beef, diced onion, breadcrumbs, garlic powder, black pepper, and salt. Mix with hands until evenly combined without overworking the meat.
Shape mixture into 4-6 evenly sized patties, about 3/4 inch thick. Place patties in the prepared baking dish.
In a separate bowl, whisk together cream of mushroom soup and beef broth until smooth. Pour evenly over the raw patties, coating each one.
Cover dish tightly with aluminum foil and bake for 35-40 minutes. Remove foil and bake for another 10 minutes until patties are cooked through and sauce is bubbling.
Let rest for 5 minutes before serving. Garnish with fresh parsley and serve over mashed potatoes, rice, or noodles.