Preheat your oven to 400°F. In a skillet over medium heat, warm the olive oil. Add the diced onion and cook until soft, about 4-5 minutes. Then add the minced garlic and cook for 30 seconds until fragrant. Transfer the mixture to a large bowl.
Add the ground beef, breadcrumbs, Parmesan, Italian seasoning, milk, 2 1/2 tablespoons of ketchup, Worcestershire sauce, eggs, salt, pepper, and cheddar cheese cubes to the bowl. Gently mix until just combined, making sure not to overmix.
Shape the meat mixture into a loaf on a baking sheet lined with parchment paper. Spread the remaining ketchup on top.
Bake for 40-45 minutes or until the internal temperature reaches 160°F. For a glazed finish, spread additional ketchup on top of the loaf toward the end of baking. Once baked, allow the meatloaf to rest for 5 minutes before slicing and serving. Sprinkle with chopped parsley if desired.