Heat a dutch oven or stock pot over medium heat. Add butter; melt.
Add sliced onions, pepper and garlic powder; sauté for 7-8 minutes until tender.
Add beef broth, Worcestershire sauce and salt to taste. Bring to a simmer, cover and simmer for at least 10 minutes. Keep warm until ready to serve.
Just before serving, preheat broiler.
Arrange oven-proof individual crocks, bowls or soup mugs with a wide mouth on a baking sheet.
Ladle soup into bowls. Top each with a slice of toasted bread and a slice of cheese.
Place under broiler until cheese melts and is slightly golden. Serve warm.
