Liberally season pork on all sides with rub. Rub into the pork. Wrap in plastic wrap or place into an airtight container and chill overnight.
Preheat oven to 300°F. Fit a rimmed pan with an oven safe rack. Unwrap pork butt and center on rack fat side up.
Meanwhile, place sauce ingredients into a saucepan. Bring to a boil and immediately remove from heat. Reserve 2 cups for serving. (You may strain using a fine mesh sieve to remove pepper flakes, if desired)
Roast pork for 6-7 hours basting with sauce every hour. Cook until it reaches an internal temperature of 200°F and the pork is falling apart. Rest uncovered for 20-30 minutes.
Shred cooked pork using 2 forks removing all visible fat and bone. Drizzle with small amount of reserved sauce then serve remaining on side.
Serve on kaiser rolls, hamburger buns or Texas toast with cole slaw.