Saute onions in margarine in large saucepan 10 minutes or until tender.
Add broth, water and pepper.
Cover; simmer 15 minutes.
Pour soup into six 8-ounce ovenproof serving bowls; top with bread slices.
Cover with Swiss and parmesan cheeses.
Place bowls on jelly roll pan.
Broil 3 minutes or until Swiss cheese is melted and golden brown.