In a bowl, mix the minced garlic, oregano, cumin, paprika, salt, pepper, and cayenne pepper (if using). Add the sour orange juice and olive oil, mixing well to form a paste.
Rub the marinade all over the pork shoulder, making sure to get it into any crevices. Place the pork in a large resealable plastic bag or a covered dish. Refrigerate for at least 4 hours or overnight for the best flavor.
Preheat your oven to 325°F (165°C).
Remove the pork from the marinade and place it in a roasting pan. Scatter the chopped onion and bell pepper around the pork. Pour the chicken broth into the pan.
Cover the roasting pan with aluminum foil and roast the pork in the preheated oven for about 3-4 hours, or until the meat is tender and easily pulls apart. Remove the foil during the last 30 minutes of cooking to allow the skin to crisp up.
Once cooked, remove the pork from the oven and let it rest for about 15 minutes before carving. Serve with rice, beans, and your favorite side dishes.
Enjoy your meal!