Preheat your oven to 350°F (175°C). Prepare a baking pan by lining it with aluminum foil and spraying it lightly with cooking spray.

In a medium skillet over medium heat, melt a tablespoon of butter and sauté the diced onion for about 5-7 minutes until translucent.

In a large mixing bowl, combine eggs, milk, and Italian bread crumbs. Let it sit for 5-10 minutes to create a moist base.

Add the cooled sautéed onions to the mixture along with the lean ground beef, ketchup, Italian seasoning, parsley, salt, and pepper. Mix gently.

Transfer the meat mixture into the prepared baking pan, shaping it into a loaf.

Bake the meatloaf in the oven for 40 minutes.

While baking, mix the remaining chili sauce with ketchup and brown sugar in a small bowl.

After 40 minutes, spread the prepared sauce over the top and return to the oven for an additional 15-30 minutes.

Optionally broil for 1-2 minutes for caramelization.

Let the meatloaf rest for 10 minutes before slicing.