Preheat your oven to 350°F (175°C). Line a baking pan with aluminum foil and coat with non-stick cooking spray.

Sauté the diced onion in a skillet over medium heat for 5-7 minutes until tender and translucent. Let cool.

In a large mixing bowl, combine the eggs, milk, and Italian bread crumbs. Let sit for 5-10 minutes.

Add the sautéed onions, lean ground beef, ketchup or chili sauce, Italian seasoning, parsley, kosher salt, and black pepper to the breadcrumb mixture. Mix gently.

Transfer the meat mixture to the baking pan and shape it into a loaf.

Bake in the preheated oven for 40 minutes.

While baking, mix together chili sauce and ketchup, adding brown sugar if desired.

After 40 minutes, remove meatloaf and spread the glaze over the top. Return to the oven for another 15-30 minutes.

Let the meatloaf rest for at least 10 minutes before slicing.