Heat the oven to 350 degrees. Sear the whole tenderloin on all sides in a hot, nonstick skillet. Remove from the heat and season with the pepper and red pepper flakes.

Cover the tenderloin with foil and bake for 25 minutes. Heat the oil in a medium saucepan and saute the onion and garlic for 5 minutes.

Add the barbecue sauce, catsup, water, and vinegar. Simmer for 10 minutes. Shred the pork with 2 forks. Add the pulled pork to the sauce. Serve on buns.