Use boiling beef, chuck or brisket or any cheaper cut of meat!
3 to 5 lb roast .... using large knife to cut slits completely through the meat, insert slivers of garlic down into the slits. Can use onion instead. Both may be used.
Pour one (1) cup of vinegar over the meat nad make sure it runs down into the little slits. Put into fridge and leave it for 24 to 48 hour.
When ready to cook, place a bit, heavy pot --iron if possible -- an brown in oil until nearly burned on all sides. Pour two cups strong black coffee over the meat. Add two cups water and cover. Simmer on top of the stove for four to six hours. Season with salt and pepper twenty minutes before serving time. This roast falls apart with the touch of a fork, no matter how tough your meat originally was. And the yummy black gravy that you get will put those mashed potatoes on cloud nine. If you like lots of gravy, some water may be added.
Another thing; if you cook your roast too fast or the lid is not tight enough, you may need additional water. However, don't let the roast swim as if it were a whale in the Pacific! Never more than one cup of water at a time after the mix has began to boil down.