If you’re not a habitue of hole-in-the-wall taquerias, you may never have encountered tacos al pastor, a staple of places serving humble Mexican fare. They’re made of meat cut from a rotating vertical cone—cooked by a central heating element—in the style of Greek gyros or Middle Eastern shawarma, sometimes crowned with a hunk of pineapple or onion. The meat’s sliced rather than ground, and unlike shawarma, it’s usually pork, marinated in vinegar, spices, and orange red achiote.

The origins of tacos al pastor are uncertain. Some theorize the dish arrived in Mexico with Lebanese immigrants who originally used lamb. El Tizoncito, a quick-service chain based in Mexico City, claims to have invented it about 30 years ago. Wherever it came from, getting it right isn’t easy. A restaurant requires substantial traffic to keep the spit turning and the meat fresh. And the simplicity of shepherd-style tacos may be a touch declasse for upscale places that serve them, like Adobo Grill (1610 N. Wells, 312-266-7999), though Rick Bayless is on record as loving them.

At Taqueria Moran (2226 N. California, 773-235-2663), tacos al pastor (called adobado on the menu) are griddled, but no hot surface can produce the delicate browning and lush juiciness that comes from spit-grilled meat. On a griddle the heated meat releases its essence onto the hot surface, where it sizzles away; on a vertical spit, juices run slowly to the bottom, passing over the length of the meat and basting it. The slices’ irregularity and the way they’re crunchy outside and moist inside make the taco less predictable and more interesting. When prepared the right way the meat has a sweet heat that gives each bite a lot of dimension and makes the taco an excellent fistful of food.

El Burrito Amigo (5238 W. Grand, 773-637-2188) fires up the spit Monday through Saturday between 5 and 9 PM. If you’re lucky you’ll get the meat right off the cone; when the fire is turned down the pork is cut off the spit and griddled to ensure, as the owner told me, that it “cooks all the way through”—not an unreasonable precaution. But whenever you arrive, expect full-dress tacos loaded with onions both grilled and raw (atypical but nice), fresh cilantro, and radishes. The sharpness of the garnishes balances the richness of the pork, which is slightly underseasoned for my taste.

The sign in front of Taqueria El Pastor (4418 W. 63rd, 773-284-1003) shows a hand slicing meat from a flaming cone, but before you enter, peek in the front window and make sure the spit is spinning. To have your taco al pastor carved fresh, ask for it that way; standard operating procedure here again seems to be to griddle the meat before serving. On a recent visit I got several tacos of excellently broiled meat, tender yet well textured, and requiring just a squirt of hot sauce for extra piquancy—perhaps not perfection, but damn close.

A sign in the window at nearby Mario’s Tacos (4540 W. 63rd, 773-582-8226) proclaims that the restaurant specializes in tacos al pastor, but the meat was sitting cold on the spit, waiting to be warmed on the griddle. I took a pass.

If you go by Birria Huentitan (4019 W. North, 773-276-0768) after midnight you’ll see the butchers in back, chopping steak for carne asada and building layered mounds of seasoned pork. A shimmering shaft of meat for the tacos al pastor is usually turning and browning in the window of this modest palace of animal protein—a vegetarian might want to cross the street to avoid it. Strangely, the rule here is to serve customers from a hot tray where the freshly cut meat is deposited; if you know any Spanish, I’d recommend asking for the just-cut stuff.

Taqueria Amigo Chino (5601 W. Irving Park, 773-685-4374) is a cozy, bustling, cash-only neighborhood joint. Complimentary chips come with three stellar salsas: a sparkling house-made pico de gallo, a creamy orange one that delivers a clean burn, and a marvelous green jalapeno number. Any of them is a fine accompaniment to the tacos al pastor, which are cut straight from the spit to your plate and are quite delicious.

Like other branches of this mini empire, the Taqueria Atotonilco at 5656 S. Kedzie (773-436-4890) serves just a few things, mostly tacos and tortas from a roster of ingredients including head and tongue as well as avocado and frijoles. Tacos al pastor are the obvious standout—to watch the spitted meat spin is to witness a thing of beauty, the layers of pork bubbling, oozing seasoned juices and caramelizing on the outside. Taqueria Atotonilco offered what was, for me, the paradigmatic taco al pastor, well seasoned, spitted, and carved fresh from cone to taco. Perhaps I got lucky; your experience may vary, because it’s clear that the apotheosis of this hearty taco can be elusive, requiring a harmonic convergence of elements and actors: you have to be at the right place at the right time, when the right countermen are working. Of course, any taco al pastor would be even better on house-made tortillas, but that’s a vision of perfection I’ve yet to find here.

For more on food and drink, see our blog The Food Chain at chicagoreader.com.