Lebanese immigrants introduced spit-roasted meats known as shawarma to Mexico in the 19th century, and eventually tacos al pastor came to be. The dish consists of chili-seasoned spit-roasted pork shaved into thin slices and served in corn tortillas along with chopped pineapple, onion and cilantro. For our simplified version, we use pork tenderloin that has been pounded, briefly marinated and grilled. Chopped grilled pineapple tossed with fresh cilantro completes the tacos, along with a sprinkle of chopped white onion and, if desired, shredded red cabbage. To help simplify prep, purchase an already peeled and cored pineapple. The four chipotle chilies in this recipe yield medium-hot spiciness; if you like, reduce the heat by using only two or three. Leftover pork does not keep well because the raw pineapple will break down the meat. If you don't plan to serve all of the pork, set some aside before adding the sauce at the end.