Combine the salt, pepper, chili powder, garlic powder, and cayenne. Rub the pork shoulder roast all over with the spice mixture. Wrap the pork in plastic wrap and refrigerate for an hour.
Preheat the oven to 300 F.
Heat the oil in a large Dutch oven over medium heat. Sear the roast on all sides, about 12 to 15 minutes total.
Remove the roast to a plate and set aside.
Add onions to the pan and cook, stirring, until lightly browned. Add the garlic and cook, stirring, for 2 minutes.
Add the roast and the beer to the pan and bring to a boil.
Cover the pan and transfer to the oven.
Cook for 3 to 4 hours, until the roast is very tender and falling apart.
Remove the roast and shred.
Serve with barbecue sauce in split toasted buns or in tortillas with taco sauce or salsa and toppings.
Notes
Nutritional information is based on a third-party application and should be considered an estimate. Values may differ depending on brands, ingredient measurements, and serving variations.