Preheat your oven to 350°F (175°C). Line a rimmed baking pan with foil for easy cleanup.

In a skillet, melt butter over medium-low heat. Add diced onion and sauté until tender, about 5-7 minutes.

In a bowl, combine eggs, milk, and Italian breadcrumbs. Let sit for 5-10 minutes.

Add ground beef, sautéed onions, ketchup, Italian seasoning, parsley, salt, and pepper. Mix gently until combined.

Transfer mixture to the baking pan, shaping it into a loaf roughly 2 inches tall.

Bake in the oven for about 40 minutes, until edges are brown.

Mix chili sauce with ketchup in a bowl. Once the meatloaf has baked for 40 minutes, spread the sauce on top.

Return the meatloaf to the oven for an additional 15-30 minutes until the internal temperature reaches 160°F.

Let the meatloaf rest for about 10 minutes before slicing.

Slice and serve warm, ideally paired with mashed potatoes or veggies.