1. In a skillet over medium-low heat, add olive oil and sliced onions. Cook slowly for 30–40 minutes, stirring occasionally. Deglaze with beef broth halfway through for rich flavor.

2. In a large mixing bowl, combine ground beef, minced garlic, breadcrumbs, eggs, Worcestershire sauce, chopped thyme, salt, and pepper. Mix just until combined—do not overwork.

3. Press the meat mixture into a 9×5 loaf pan. Bake at 375°F (190°C) for 35–40 minutes, or until the internal temperature reaches 155°F.

4. Remove from oven. Lay Swiss cheese slices on top, then spoon the caramelized onions over. Return to oven for 10 more minutes until cheese is melted and bubbly.

5. Let the meatloaf rest tented with foil for 10 minutes. Slice and serve with pan juices, mashed potatoes, or fresh bread.