1. Preheat your oven to 300°F (150°C).
2. In a large Dutch oven, combine pork, salt, pepper, cumin, oregano, orange juice, lime juice, garlic, and onion.
3. Bring the mixture to a simmer over medium-high heat.
4. Cover the Dutch oven and transfer it to the preheated oven. Cook for about 4 hours, or until the pork is tender and easily shredded.
5. Remove the pork from the oven and shred it using two forks. Return the shredded pork to the Dutch oven and mix it with the juices.
6. Increase the oven temperature to 425°F (220°C). Spread the shredded pork evenly in the Dutch oven and cook, uncovered, for an additional 15-20 minutes, or until the edges are crispy.
7. Serve the carnitas hot with tortillas and your favorite toppings.