Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper.
In a large skillet, heat the olive oil over medium heat. Add the sliced onions and cook, stirring occasionally, until caramelized, about 20 minutes.
Add the minced garlic, dried thyme, salt, and pepper to the onions and cook for another 2 minutes. Remove from heat and let cool slightly.
In a large bowl, combine the ground beef, breadcrumbs, grated Parmesan cheese, beef broth, beaten eggs, and half of the caramelized onions. Mix until well combined.
Shape the meat mixture into a loaf and place it on the prepared baking sheet.
Spread the remaining caramelized onions over the top of the meatloaf and then spread the ketchup over the onions.
Bake in the preheated oven for 45-50 minutes, or until the meatloaf is cooked through.
Remove from the oven and let rest for 10 minutes before slicing.
Garnish with fresh parsley before serving.
