Step 1: Caramelize the Onions
In a skillet, melt butter and heat olive oil over medium-low heat. Add the sliced onions, sprinkle with salt, and stir occasionally. Cook the onions slowly for 40-60 minutes, until they turn a deep golden brown. If they begin to stick, add a splash of water. Once done, set the onions aside.

Step 2: Prepare the Meatloaf Mixture
Preheat the oven to 375°F (190°C). In a large mixing bowl, combine ground beef, breadcrumbs, eggs, broth (or milk), Worcestershire sauce, garlic powder, onion powder, thyme, salt, and pepper. Mix gently to avoid overworking the meat. Then fold in the caramelized onions and shredded cheese, if desired.

Step 3: Shape and Assemble the Meatloaf
Line a baking sheet with parchment paper or grease a loaf pan. Shape the meat mixture into a loaf and place it on the prepared baking sheet or in the pan.

Step 4: Apply the Glaze
In a small bowl, combine ketchup, Worcestershire sauce, brown sugar, and Dijon mustard. Brush the glaze generously over the top of the meatloaf.

Step 5: Bake
Bake for 60-70 minutes, or until the meatloaf reaches an internal temperature of 160°F (71°C). Once done, let the meatloaf rest for 10 minutes before slicing and serving.