Whisk the egg yolk in a medium-sized bowl until lightly mixed. Add the Parmesan cheese, parsley, Italian seasoning, salt, garlic powder, and black pepper, and whisk to combine.
Add the ground beef to the egg mixture. Use your hands or a large spoon to thoroughly mix the egg mixture into the ground beef.
Add the onions and breadcrumbs. Mix them into the meat using your fingers or the spoon.
Pour the oil into a small baking dish, swirl to coat the bottom of the dish. Form the ground beef mixture into a large ball and place in the center of the baking dish. Top the meatball with tomato sauce.
Place the baking dish in the oven and cook for 20 minutes. (The meatball is done when cooked through, and when it reaches an internal temperature of 165° F on an instant-read thermometer.)
Remove from the oven and top with 1 Tablespoon of Parmesan cheese. Cover baking dish with a sheet of aluminum foil and let rest for 10 minutes. Enjoy hot.
Notes
Expert Tips
When mixing the ingredients, avoid overworking the meat to ensure a tender meatball.
For optimal cooking, ensure the oven is preheated fully before baking.
Letting the meatball rest for a few minutes after baking allows the juices to redistribute.