Preheat the pellet grill to 225 degrees Fahrenheit. Put the beer, orange juice, lime juice and garlic into a large grill safe disposable pan. Add thinly sliced onions to the pan.
Brush pork with olive oil, completely covering.
In a mixing bowl combine the rub ingredients. Rub all over the pork.
Place the seasoned pork in the pan.
Cook on a preheated pellet grill for 4-5 hours or until it reaches an internal temperature of 165 degrees Fahrenheit.
Carefully remove the pan from the grill and place pork shoulder on a cutting board. Cut the meat into 2-3 inch pieces, being sure to keep the pieces evenly sized. Return the pork chunks to the pan.
Cover the pan with aluminum foil and return to the pellet grill. Turn the temperature up to 350 degrees Fahrenheit and cook for about 2 hours until the meat reaches an internal temperature of 195 degrees Fahrenheit.
Remove the tinfoil from the pan and allow the meat to rest for about 30 minutes.
Take pork out of the pan, reserving the juices in the pan, and shred the pork.
After the pan of juices has set, skim off the fat from the top and remove any fat from the pan.
Next, drizzle some olive oil in a cast iron skillet. Heat the pan on your stove top over medium-high heat or place it back on the smoker at a temperature of 400 degrees Fahrenheit.
When the oil is hot, place the smoked pulled pork along with a couple Tablespoons of reserved juices in the skillet. Cook until the bottom of the meat is browned. Serve with tortillas and toppings.