Heat oil in a large heavy based saucepan, brown pork on all sides and remove. Add onion, garlic, and spices to pan, cook until fragrant and onion is translucent, add pork back into the pan with tomatoes, orange juice and 1 cup of water. Cover and simmer for 2 hours, turning occasionally and topping up with more water if necessary.
Remove pork, and rest for 5 minutes before shredding with two forks, discarding fat.
Increase heat to medium and reduce sauce until very thick, stir in shredded pork.
Serve pork wrapped in tortillas with pineapple, coriander sprigs, a generous dollop of sour cream and a squeeze of lime juice.