Preheat oven to 325 degrees F (165 degrees C). Cut French baguette bread into slices about 3/4 inch thick and place directly on rack in oven for 20 minutes or until bread is dry and lightly browned. Remove and set aside.
Melt butter or margarine in a heavy bottomed saucepan, add onions and cook over low heat, stirring occasionally. Cook until onions are golden brown, about 15 minutes. Sprinkle onions with flour and cook, stirring for about 2 minutes or until flour is well blended.
Add beef consomme, water, salt, pepper, garlic powder, ketchup, Worcestershire sauce and beef bouillon cube; bring to boil and simmer for 20 minutes.
In a mixing bowl, combine Cheddar, Swiss and Parmesan cheese.
Set oven temperature to broil. Ladle soup into oven-proof soup bowls and top each bowl with a slice of toasted French baguette bread. Sprinkle mixed cheese over bread and place one slice of Gruyere cheese on top. Place soup bowls under broiler and broil until cheese is melted, bubbly and lightly browned, about 2 to 3 minutes. Serve immediately.