Poke holes all over the pork with a fork. Rub achiote paste all over the pork, and set aside. In a large bowl, mix together the orange juice, lemon juice, and habanero peppers. Mix in the cumin, paprika, chili powder, coriander, salt and pepper. Place pork in the mixture, cover, and refrigerate overnight, turning two or three times.
Preheat the oven to 325 degrees F (165 degrees C). Wrap the pork and marinade in aluminum foil or banana leaves that have been soaked in water for 30 minutes. Place into a casserole dish, and cover.
Bake for about 2 hours, until the meat falls off the bone. The slower you cook it, the better it is. You could also bake it in a 200 degrees F (95 degrees C) oven for 4 or 5 hours, or in a slow cooker without the foil or leaves.
While the pork is cooking, make the sauce. Bring the red wine vinegar to a boil in a small saucepan. Add onions, reduce heat to medium-low, and simmer until tender. Pour sauce over pork, and serve with white rice and corn tortillas. Each person can make tacos or fajitas with the pork, the rice and the sauce.
