A proper cemita relies on papalo, a pungent, citrusy herb almost never used outside Puebla, which locals say cannot be substituted with cilantro without ruining the sandwich.
A soft, sesame-seed egg bread roll is stuffed with breaded milanesa, quesillo cheese, avocado, chipotle peppers, and the herb papalo. Puebla's covered markets, especially Mercado La Victoria, are lined with stalls dedicated entirely to cemitas.