Slice the onions thinly & sauté them in butter or olive oil over medium-low heat. Cook for about 20-25 minutes until they turn golden brown & sweetly fragrant. Season with salt & pepper, then allow to cool.
Meatloaf
Preheat oven to 350 F.
In a large mixing bowl, combine the ground beef with half of the caramelized onions, garlic powder, onion powder, dried thyme, Worcestershire sauce, egg, & breadcrumbs. Mix gently until just combined to keep the meatloaf tender.
Transfer the meat mixture into a greased loaf pan. Shape it into a loaf & bake for 45-50 minutes, or until the internal temperature reaches 160°F for safe consumption.
Once baked, take the meatloaf out of the oven & pile the remaining caramelized onions on top. Sprinkle the Gruyere cheese generously over the onions. Return to the oven for another 10-15 minutes until the cheese is melty and bubbly.
Allow the meatloaf to rest for about 5 minutes before slicing. This helps maintain its juiciness. Serve while hot, alongside creamy mashed potatoes or a salad.