Preheat the oven to gas 3, 160°C, fan 140°C. Put a flameproof casserole over a medium/high heat then add the oil. Season the pork then brown it in batches and set aside on a plate. Turn the heat down, add the onion and garlic, then soften in the remaining fat for 5 minutes.
Stir in the spices and oregano till fragrant, then add the vinegar and return the meat to the pan. Pour in 400ml water (or enough to come half way up the top pieces of meat), cover the pan leaving a small gap for some steam to escape, then cook in the oven for 2 hours, or until the pork is meltingly tender.
30 minutes before serving, toss the red onions with the lime juice and the pinch of paprika and leave in the fridge to soften.
Remove the pork to a board or plate using a slotted spoon, spoon away any excess fat from the sauce, then boil it for a few minutes until slightly thickened and tasty. Season to taste. Shred the pork using two forks, then serve in the warmed tortillas, with a spoonful of the sauce, some onions and a few sprigs of coriander.
Only meat reared to RSPCA standards gets the Freedom Food label. Find out more about Freedom Food.
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For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.