Heat a 10” cast iron griddle pan on medium-high heat.*
Brush a thin layer of olive oil over the pork and then rub it with a generous amount of the rib seasoning, making sure all sides are generously coated. Then Sear the pork on all sides, about 1 minute per side.
Line a slow cooker with half of the sliced onion, add the pork, and top with remaining onion. Pour the beer over the pork and cook for 8 hours on low.
When the pork is ready, remove it from the slow cooker and shred using two forks.
Notes
If you don't have a cast iron griddle pan, a heavy bottom pan will work.