If grilling or roasting in the oven, slice pork shoulder into 1/4 inch slices. For other methods, trim fat from the pork shoulder and cut meat into 3 to 4 inch chunks.
Chile powder
If using your own chili powder, skip this step and make the marinade. Using gloves, remove the stems and scrape out the seeds from the dried chiles. Toast over low heat in a dry skillet for a few minutes. Allow chiles to cool, then grind to a powder in a spice/coffee grinder. Alternatively, soak the peppers in hot water for 20 minutes, then blend with the marinade ingredients.
Marinade
To a blender, add the chili powder, achiote paste, onion, pineapple juice, vinegar, garlic, salt, Mexican oregano, cinnamon, clove and epazote (optional). Blend until pureed.
If grilling or roasting in the oven, slice pork shoulder into 1/4 inch slices. For other methods, trim fat from the pork shoulder and cut meat into 3 to 4 inch chunks. Place pork in a sealable food storage bag or container that can be covered with a lid. Pour the chile marinade over the pork. Wearing kitchen gloves, use your hands to toss the chile marinade and pork together, then cover container. Chill in refrigerator a minimum of 4 hours, or up to 10 hours. Allow meat to come to room temp prior to cooking.
For the Grill or Smoker: (See Note 5)
Preheat grill to 250°F. Shake off excess marinade. Place cut pineapple bottoms into a cast iron skillet or shallow baking pan. Insert a wooden or metal skewer or long wooden chopstick through the center of the pineapple. Start layering slices of marinated pork, repeating until meat is used, or you have 1 inch of skewer left. Leave 1 inch of skewer on top and cap it with trimmed pineapple top.
Grill at 250°F for 3 1/2 hours, or until internal temp reaches 145°F-150°F. (See Note 5). Start basting with pan juices in last hour. Outside should be caramelized and crispy. Use a sharp chef's or serrated knife to slice meat in downward motion. Put pan back on grill to crisp up the edges as you continue to slice remaining meat.
Oven Method #1: slices
Remove all racks except bottom one from oven. Preheat oven to 250°F.
Assemble meat onto skewers as described in Grilling instructions, above. Slow roast pork in oven for 3 1/2 hours, or until internal temperature reaches 145°F-150°F. Start basting with pan juices in last hour. Outside should be caramelized and crispy. Use large chef's knife to slice meat in downward motion. Put pan back in oven to crisp up the edges as you continue to slice remaining meat if you'd like.
Oven Method #2: chunks
Preheat oven to 250°F. Shake off excess marinade and cut pork into 3 to 4 inch chunks. Transfer to an 11x13" roasting pan or stone bakeware dish
Slow roast at 250°F covered with aluminum foil for 5 hours, or until internal temperature reaches 145°F-150°F. Remove the aluminum foil and continue roasting for 1 hour or until completely tender when pulled with a fork.
Instant Pot (Pressure Cooker)
Shake off excess marinade and cut pork into 3 to 4 inch chunks. Place marinated pork chunks and remaining marinade in the pressure cooker. (See note 6). Attach lid and set valve to "sealing". Press Manual and High Pressure settings, then use the [+] button to choose 25 minutes pressure cooking time. When done, allow a Natural Pressure Release for 15 minutes, then release any remaining pressure from pressure cooker.Remove pork chunks and transfer to a baking dish or stoneware pan. Broil in oven uncovered for 10 minutes to render fat and crisp up edges. Check that internal temperature reaches 145°F-150°F.
Slow Cooker Method:
Shake off excess marinade and cut pork into 3 to 4 inch chunks.Place marinated pork chunks and remaining marinade in the slow cooker. Cook for 4 hours on high or 8 hours on Low, or until internal temperature reaches 145°F-150°F. Remove meat from slow cooker and transfer to a baking dish or stoneware pan. Broil uncovered in oven for 10 minutes to render fat and crisp up edges.
Serving:
Serve in small tortillas topped with chopped onion, cilantro, squeeze of lime juice and hot salsa. I like diced pineapple on top as well, but this is optional.
Video
Notes
I used 1 large pineapple. Trim the green top off and cut the top about 2 inches down and do the same from the bottom. These will be the bases for the skewers to stand in and the meat is then placed on top. Top the meat with 2 more 2-inch pieces of trimmed pineapple rings (as seen in video). The remaining is trimmed, diced and used for serving (about 1 1/2 cups).
Achiote paste can be found in most Mexican markets, or you can make your own achiote paste. It creates the authentic deep red color and flavor that al pastor is known for.
Mexican oregano is a relative of Lemon Verbena and is native to Mexico, with notes of mild licorice and citrus. Mediterranean oregano is a member of the mint family and most often is used in Greek and Italian recipes. Mediterranean oregano is the one most found in spice racks at supermarkets.
Epazote is similar to oregano and fennel with minty notes. It’s found in Mexican cooking and is typically used in beans for flavor and helping reduce their tendency to cause flatulence.
I grill in a Traeger smoker on the lowest rack because it allows me to fine tune and control the heat at lower temperatures better than regulating a charcoal or gas grill. When grilling, times may vary depending on what type of grill you are using. Pork is done when internal temperature of pork is is 145°F to 150°F.
I have an earlier model Instant Pot (December 2015) that is not as sensitive as newer models that show the BURN notice quite easily. If that happens to yours, add 1/2 cup to 1 cup of chicken stock if needed.
Figure each pound of pork feeding 3 people, so depending on how much you serve per person this 5 pound recipe serve anywhere between 12-15 people.