Get a piece of pork shoulder and cut it up into 2" or so chunks. Toss in a bowl with a heavy amount of chile powder (like California, paprika, and chile de Arbil (spicy)), a little salt, and maybe a little garlic powder and tomato paste.
Fry the chunks in a pan with some olive oil, then remove them to a separate bowl. Work in small batches, and get the pieces nice and brown all over.
Cook until the tomatoes are dry and starting to brown a little, then add a few spoons of enchilada sauce to the pan along with the meat. Cook everything down again until the enchilada sauce is dry, then pour in the rest of the tomato juice along with about 2/3 of the enchilada sauce and a can of water.
Bring the liquid to a boil and put the whole pan into the oven at 275, with a lid on.
Cook for around 4-5 hours until the pork is very tender, then take the lid off and turn the oven up to 350 for another 30-60 minutes, so the top can brown.
We took the meat out and poured the sauce into a jar so we could spoon off the extra pork heaven, then poured the sauce back over the meat.
This is awesome in tacos or over rice along with limes and sour cream.