Cut the pork butt into 4 equal pieces and season well and evenly with the rub mixture, literally giving each side a few good rubs to work in the seasoning. (This should use up a little more than half the total rub.)
While the meat is absorbing the seasoning and coming up to room temperature (at least 30 minutes out of the fridge), preheat the oven to 425 and make the sauce. (Directions to follow.)