In a medium-sized bowl, mix together brown sugar, ground cumin, oregano, salt, garlic powder, pepper, and paprika. Stir in 2 Tablespoons of olive oil.
Pat the roast with a paper towel to absorb any excess moisture. Rub the seasoning mix all over the pork butt, then place it in the slow cooker, fat on top.
Deseed and slice up the jalapeno pepper. Dice the onion. Add them to the slow cooker on and around the roast.
Halve the orange and lime and squeeze the juices over the roast, add the juiced halves to the slow cooker.
Slow cook the roast on high for 8 hours.
Remove the roast from the pot and place it onto a cutting board. Allow it to rest for 10 minutes. Then shred using meat shredders or 2 forks.
Add the remaining 1 Tablespoon of olive oil to a large skillet over high heat.
Caramelize the pork by frying it (in batches- so as not to crowd the meat). Place about ¼ of the shredded pork and about ¼ cup of the juices from the crockpot in the skillet. Press the meat onto the bottom and allow it to sear. Continue this until all of the meat has been seared until slightly crisp.
Place the seared meat into your serving container. Serve the meat drizzled with some of the remaining juices from the crockpot if desired.