Al pastor is Mexican shwarma.

Literally. A vertical spit loaded with marinated meat, rotated while carving off crisped exterior was carried from Lebanon to Mexico, and over time the ingredients changed until it was pork marinated in a wet annatto-heavy spice mix instead of lamb in a drier, herby mix, corn flatbread instead of wheat, salsa instead of toum, et cetera.

They affix a trimmed cylinder of pineapple at the top of the trompo (loaded spit), and skilled chefs learn to cut thin slices of the pork into a small tortilla, then cut a slice of pineapple with a knife-flick such that the sliver lands in the taco held in their off hand.