For rub, in a small bowl combine chilli powder, kosher salt, oregano, black pepper, cumin and cayenne pepper. Sprinkle rub over all sides of meat and rub in with your fingers. Place meat on a rack in a shallow roasting pan. Roast for 25 to 35 minutes or until thermometer registers 155oF. Cover meat with foil and let stand for 15 minutes before slicing. The temperature after resting should be 160oF.