Preheat the oven to 350F and line a 15 by 10 inch rimmed baking sheet with foil or parchment.
In a medium bowl, combine the ground beef, parsley, Parmesan, almond flour, egg, salt, pepper, garlic powder, onion powder, oregano, and water. Mix thoroughly by hand until well combined.
Form the meat mixture into 12 meatballs about 2 inches in diameter and place them 2 inches apart on the sheet pan. Bake 20 minutes.
Place the meatballs in a casserole dish large enough to fit them all. Spoon the marinara evenly over, then sprinkle the cheese overtop. Bake another 20 minutes, or until the meatballs are cooked through, the sauce is bubbling, and the cheese is golden. Garish with chopped fresh parsley, if desired.