Start by thinly slicing the yellow onions and layering them in your crockpot. Pour in the beef broth and add a splash of Worcestershire sauce to enhance the flavors. Stir gently to combine.

In a large mixing bowl, combine the ground beef, dry onion soup mix, breadcrumbs, minced garlic, eggs, milk, ketchup, Worcestershire sauce, thyme, salt, and black pepper. Mix gently to avoid overworking.

Form the meatloaf mixture into a loaf shape and place it over the onions in the crockpot.

Cover the crockpot and cook on low for 6–7 hours or on high for 3–4 hours, ensuring it reaches 160°F for doneness.

In the last 10 minutes, sprinkle cheese on top and cover until melted.

Allow the meatloaf to rest for 10 minutes before slicing and serve with the onion mixture spooned over each slice.