Sometimes for lunch I will go to a little dive called "El Fogón de Pepe" (Joe's Oven). It's basically a "taquería"... taco restaurant. It's not my favorite taco joint in Mexico City, but the food is decent and it is close to where I am staying.
For about $4 US I can get a glass of jamaica (iced hibiscus flower tea), a bowl of soup, and two or three "tacos al pastor".
"Tacos al pastor" (shepherd-style tacos) are one of the most popular varieties of tacos in Mexico City. It originated with Lebanese immigrants to Mexico City. Their cuisine includes shawarma, lamb that has been roasted on a spit. The Mexicans took that idea, but substituted pork for lamb.
The pork is marinated with chile peppers, spices and pineapple. It is placed on a vertical spit called a "trompo", and roasted with a gas flame. The meat is sliced off the rotisserie, and served on a corn tortilla with chopped onion and cilantro. Bowls of sauces and lime wedges are served on the side. It is a very tasty snack.