Slice onions. Heat oil over medium heat then sauté the onions until translucent, about 5-7 minutes.
Blend tomatoes, lime juice and chipotles until smooth.
Add tinga sauce and salt to the onions, then stir!
Add shredded chicken and stir. Add chicken broth if needed to thin the mixture.
Place meat on a tostada then top with desired toppings. We like lettuce, cilantro, cotija and avocados!