I love the sweetness of onions in omelette but have never thought of mozzarella. Did you put it under a grill or put it in cold?
Might be an idea for me to try that with a sort of Spanish tortilla ie perhaps with some potato added and red pepper covered with lots of fried onion with the cheese on top and grilled.
What do you reckon?
The onions and mozzarel' were placed on the omelette as it was being prepared. The cheese was salted, as previous experiences with the unsalted variety have been underwhelming (those are best saved IMO for a caprese salad, or a prosciutto sandwich...).
Indeed a Spanish tortilla needs potatoes and onions, and adding the cheese sounds quite nice, though rich! Take a picture if you do thus.
By the by, I seem to notice more and more signs in New York City for fried onions (on hot dogs, for example). That sounds like a fad I'd be down with (and have been down with since plopping them on top of sate and peanut sauce in Indonesia).