Combine the garlic powder, cumin, coriander, oregano, and cayenne pepper in a bowl. Thoroughly rub the spice mixture over the pork.
Place the roast in a pressure cooker with the beef broth, bay leaves, and onion over medium-high heat. Seal the cooker, and bring to full pressure; reduce the heat to maintain high pressure, and cook for 45 minutes.
Remove the pressure cooker from the heat and allow the pressure to drop naturally. Transfer the pork to a serving bowl and shred the meat with forks.
