Trim the fat off of the pork roast and cube the meat into 1-inch chunks. Sprinkle the meat with salt and pepper.
In the bottom of the instant pot, drizzle the oil and then place the meat on top. Add in the chopped onion, broth, garlic, lime juice, orange juice, cumin, oregano, and chili powder. Cover and lock the lid, turning the valve to sealed. Pressure cook on high for 30 minutes and allow for 15-minute natural release.
Once the carnitas has had a natural release, lightly shred the pork with two forks and place on a foil-lined baking sheet. Drizzle the top of the pork with the juices from the instant pot. Place the meat under the broiler on high for 3 minutes and then take out to stir the meat and drizzle with more juices if needed. Broil for an additional 3 minutes and then remove from the oven.
Sprinkle the meat with fresh chopped cilantro, if desired. Serve in tacos, tortas, burritos - whatever you like!