Preheat the oven to 275 degrees F.
Put the poblano and onion slices in the bottom of a heavy pot. Mix the cayenne, cumin and a pinch of salt and pepper together in a bowl, then use the mixture to season the pork shoulder. Put the pork on top of the vegetables. Add the chicken broth, jalapeno slices, lime zest and juice and orange zest and juice. Cover and cook until tender, 4 to 5 hours.
Turn the heat up to 450 degrees F, remove the lid and cook until the surface crisps slightly, 15 to 20 minutes. Remove the pork to a board and let it rest until cool enough to handle, then remove the fat and shred the meat with 2 forks.
Strain the vegetables from the sauce and set aside. Put the meat in serving dish, add the vegetables and pour over some of the sauce.
Serve the shredded pork with warm corn tortillas, radishes, pickled jalapenos, pico de gallo, hot sauce, lime wedges and cilantro leaves.