Peel the chiles and remove the seeds. Tear them into smaller pieces. Put the chiles in a bowl and cover with hot water. Soak for 30 minutes.

Slice the pork into thin slices, cutting across the grain.

Make the marinade: Chop the onion and put it in the blender. Add the soaked chiles to the blender. Add the garlic, orange juice, pineapple juice, oregano, thyme, pepper, cumin, paprika and salt. Blend until smooth.

Put some marinade in the bottom of a 9 x 13 baking dish. Lay the pork slices in a single layer on the bottom of the pan. Cover with marinade and lay a second layer of pork. Cover with the last of the marinade and let marinate in the refrigerator for a minimum of four hours.

For the tomatillo salsa: Put the tomatillos, onion and garlic in a greased baking dish and put in a 450 degree oven for 10 minutes. Put the tomatillos, onion, garlic, chipotle and pineapple juice in a blender. Blend until almost smooth. You want a little chunk left to the texture. Pour into a bowl and stir in salt and pepper to taste.

Cook the pork: Lay the pork in a grill basket. Cook over a hot grill for 5 minutes on each side and then for 1 minute more on each side. Lay the cooked pieces on a cutting board, overlapping the pieces. Cut thin strips off the row of pork.

Assemble the tacos: Heat the tortillas on a dry skillet until warm. Place a generous amount of pork on the tortilla. Put some salsa and some cilantro on top. Serve.