Trim excess fat from pork and cut in medium size pieces. Place pork in a bowl and season with annato, cumin, salt, pepper and half of garlic. Add vinegar, onions and red ají paste. Marinate for 24 hours in the refrigerator.
Sauté remaining garlic in oil in a medium size pan and add pork, half of the marinade and onions. Cover pan and cook at low heat until meat is cooked and tender. If necessary, add more hot marinade. Meat must be juicy.
Serve pork with white rice and boiled sweet potatoes, yuccas or potatoes.