Mix soup and water together in a 1 1/2 qt.glass casserole dish.
Cover frankfurters with soup mixture.
Cover and microwave 5 to 7 minutes [REHEAT-6, 8 to 12 minutes or until piping hot.
Stir once during cooking.
Place frankfurters in buns.
Spoon chili mixture over frankfurters and sprinkle with onions.
Top with cheese and lettuce.