Whisk all dry rub ingredients together and set aside.
Remove pork from fridge at least 30 minutes prior to cooking. Pat dry and season generously with dry rub.
Heat enough oil to cover in a large cast-iron or heavy bottomed pan to medium.
Sear pork on all sides. Around 30-60 seconds each.
Add sliced onion to bottom of slow cooker pot and top with pork. Pour liquid in bottom of slow cooker.
Cook on low 6-8 hours, until pork shreds easily with a fork.
Remove pork and shred, reserving liquid. Add ½-1 cup liquid back to pork (enough to keep moist, it shouldn’t be swimming in it).
