Instructions:

1. Caramelize the Onions:
   Heat olive oil in a skillet over medium heat. Add sliced onions and cook for 15–20 minutes, stirring frequently until golden and caramelized. Add garlic and thyme in the last 2 minutes of cooking. Remove from heat and let cool slightly.
2. Prepare the Meatloaf Mixture:
   In a large bowl, combine ground beef, French onion soup mix, breadcrumbs, eggs, milk, Worcestershire sauce, half of the caramelized onions, Gruyère cheese, salt, and pepper. Mix gently until just combined (avoid overmixing to keep it tender).
3. Shape & Bake:
   Preheat oven to 375°F (190°C). Transfer the mixture to a loaf pan or shape it into a loaf on a parchment-lined baking sheet. Top with the remaining caramelized onions. Cover loosely with foil and bake for 45 minutes.
4. Add Cheese & Finish Baking:
   Remove foil, sprinkle additional Gruyère on top, and bake uncovered for another 15–20 minutes until the cheese is melted and golden, and the internal temperature reaches 160°F (71°C).
5. Prepare the Gravy:
   While the meatloaf bakes, melt butter in a skillet over medium heat. Add onions and cook until soft. Stir in flour and cook for 1 minute. Gradually whisk in beef broth and Worcestershire sauce. Simmer until thickened, about 5 minutes. Season with salt and pepper.
6. Serve:
   Let the meatloaf rest for 10 minutes before slicing. Serve with warm onion gravy on the side.