In a medium bowl (I used a 4-cup glass measuring cup), combine everything except the roast; mix well.

Make the foil packet: Tear a large sheet of heavy-duty foil (mine was about 18x18) and put the roast in the center.

Bring up the top and bottom edges....

...and fold them over 3 or 4 times.

Fold up both sides 3 or 4 times.

Very carefully unfold the top (you will have to unfold all of the folds a few times) and pour in the vinegar-tomato paste mixture. Refold everything and put the packet in a baking dish to catch any leaks (and there will be some leaks).

Heat your oven to 325. Bake the roast for 4 hours. Let it rest for 10 minutes before you open the packet.

Use tongs to take the meat out of the packet, transferring it to a cutting board or plate, and cover it with foil. The meat will come apart in large pieces when you try to pick it up....oh, yeah...

Strain the cooking liquid through a fine sieve (you might have to press it through) to make a sauce. Slightly pull the meat apart with a fork and serve it with the sauce.