Cut pork into large chunks, as needed, to fit into Dutch oven
In a small bowl, mix oil, garlic, chili powder, cumin, oregano, salt and pepper. Rub pork pieces all over with spice mix and place pieces into Dutch oven.
Juice orange and 1/2 of lime and pour the juice over the pork. Cut second half of lime into 4 chunks and place around the pork. Tuck prepared jalapeno and onion around pork pieces.
Cover Dutch oven and cook on center rack of 275°F degree oven for 3 - 5 hours or until internal temperature taken with a digital meat thermometer is at least 150°F degrees. Remove from oven and allow meat to rest for 10 minutes in Dutch oven. Transfer pork to a baking sheet and shred into bite size pieces.
Preheat oven broiler to High. Place shredded pork on baking sheet under the broiler for 4 - 8 minutes until meat edges are browned and crispy.
Serve warm on tortillas with your favorite toppings.
Watch the meat under the broil carefully to keep from burning.The spices for this dish are mild. Add 1/4 to 1/2 teaspoon Cayenne to the rub for more heat.