In a large bowl, mix ground beef, soup mix, breadcrumbs, egg, milk, Worcestershire, garlic powder, onion powder, salt, and pepper until just combined.
Shape the mixture into a loaf and place it in a parchment-lined slow cooker.
Heat olive oil in a skillet, caramelize onions over medium heat for 10-15 minutes, adding beef broth if needed.
Spread caramelized onions over the meatloaf. Cover and cook on low for 6-7 hours or high for 3-4 hours, until the internal temp is 160°F (71°C).
About 10-15 minutes before done, top with Swiss cheese and replace the lid to melt.
Carefully remove the meatloaf, slice, and serve with sides like mashed potatoes or roasted veggies.