Hi! Recipe creator/contributor here. Thanks for trying the onion soup and for all the thoughtful reviews. Just a couple of comments I thought might be helpful.
The 1 teaspoon of salt in the beginning of the recipe cannot be omitted as it is necessary for the proper caramelization of the onions. However, at the conclusion of the simmering process, please be sure to taste the soup before deciding to add any more salt (or pepper).
Also, the addition of balsamic vinegar at the end is very important--not only for taste--but also because there's a chemical in red onions that tends to turn the soup gray and cloudy, and the balsamic vinegar corrects that.
Lastly, while my broiler does take 4-5 minutes to melt the cheese properly, that's probably because I place the baking sheet on a lower rack. Yours may take less time.
Well, thanks again for all your kind comments... and, enjoy!