1.
Prepare the dry rub: Combine all the dry ingredients in a small air-tight container and mix thoroughly.
2.
Preheat oven to 200 degrees F if you're not going to bother marinating the meat.
3.
Generously rub the meat with 3 or 4 tablespoons of the dry rub.
4.
On a large sheet of heavy-duty aluminum foil, place the diced onion in the center and the cut of beef on top. Pull the side of the foil up a bit or the next step will be a mess.
5.
Combine the ketchup, Worcestershire, and liquid smoke and mix until well blended. Pour over the beef and tightly wrap everything in tin foil. If you can leave it in the fridge overnight, great. If not, it'll still be durn good.
6.
Place foil-wrapped beef on a roasting pan in the oven for 8 hours or until the internal temp is around 190 degrees F.
7.
Carefully drain the liquid from the tightly-wrapped foil into a serving dish. I usually just punch a few holes in the foil with my thermometer. Add the beef and onions to the serving dish and shred if desired. Serve with plenty of cold beer, napkins, and lies about how hard this was. Maybe put a vegetable on the table if that's how you roll.