Season the chicken with the salt and pepper and cook in the preheated oil for five minutes. Add the minced red onion, and garlic after the first five minutes to retain some crispness.
Continue cooking until the juices run clear in the chicken and the majority of the liquid in the pan is reduced.
Once the juices in the pan to add the lime juice to the pan and scrape up any bits remaining on the bottom with a spatula (flavor!).
Remove all contents from the pan and place into a large bowl (including the lime juice and “bits”.)
In the bowl, toss the chicken with the chopped cilantro.
Place a tortilla on a plate: add chicken, tomatoes, mozzarella cheese, and additional lime juice to taste.