This is hands down my favourite kind of taco. The taco al pastor I had at El Trompo in Toronto is the meal that made me a taco fan all those years ago. I love the spicy taste and the way it plays off the pineapple topping. But I was super scared to post a recipe, because even though I've spent boatloads of time perfecting it there are still a couple problems.
The first problem is the obvious: taco al pastor is traditional cooked on a spit and then shaved off (much like shawarma or gyro meat, if you've ever sampled non-Mexican cuisines), but I do not have a spit handy. So alternatively, I try my best to cut the pork loin thin for marinating and cooking, then chopped the pieces small for serving.
The second problem is how to cook it. Ideally, I would do this on a BBQ. But being that my "balcony" is more of a thin awkward ledge, I don't have the space to make this happen. Instead, you can do it a couple of ways. I've broiled the meat (as seen in the picture above) and I've used my cast iron skillet. The taste is preferable on the skillet, but good lord does it get smokey. So you decide how to proceed. Either way, I think you'll enjoy it.