Preheat the oven to 375˚F.
In a small bowl, combine the chilli powder, brown sugar, cumin, salt and pepper and rub the pork tenderloin all over. (Alternatively, use your favourite dry barbecue rub.)
Set a large ovenproof skillet over medium-high heat, add a generous drizzle of oil, and brown the tenderloin on all sides.
Add the Brussels sprouts and sweet potato to the pan and slide into the oven for 20 minutes, or until the internal temperature of the pork reaches 160˚F and the vegetables are tender.
Let the pork rest for 10 minutes before slicing.