In a large bowl, combine the beef, breadcrumbs, onion, Parmesan cheese, ⅓ cup of pasta sauce, milk, eggs, salt, and pepper. Combine the mixture well (you can use your hands) and press into a 9x5x3-inch loaf pan.
Spread the remaining pasta sauce evenly over the top.
Bake for 45 minutes, or until done. The meatloaf is finished cooking when it is brown on top and has begun to pull away from the sides. Let sit for about 10 minutes before cutting into slices and serving with baked or mashed potatoes.