Slice the meat as thinly as possible and discard any connective tissue, bone and cartilage.Season the meat with salt, pepper, and oregano, coating it well, and let it rest overnight in the fridge.

Remove the meat from the liquid that would have seeped out overnight. Pat dry with a paper towel.Place the meat on a wire rack and dry in a dehydrator until it is completely dry and stiff. It took me about 8 hours. You can dry it in the oven over 200 ºF [93 ºC] until the meat is quite stiff and dry to the touch (it took me about 3 hours).

Cool meat to room temperature and store in a sealed bag in the refrigerator for up to a month.

Rinse meat in running water. Soak overnight in abundant water (about a gallon [3.8 lt]) in the refrigerator.Boil in the same water it soaked overnight until the meat is very tender. If you cook it in a pressure cooker it should take 20 minutes. In a conventional pot it should take about an hour, add water if it becomes necessary to maintain the same water level. Save the liquid to use later on.

Cool the boiled meat to room temperature and shred it.

Heat oil in a 2 quart pot [2 lt] over low heat. Add onions, cook and stir until onions become translucent. Add garlic and cook stirring until the garlic releases its aroma (about a minute).Stir in the meat and cook until it has heated through.

Mix in tomatoes and oregano and stir. Add tomato sauce and 1½ cup of water from boiling the meat (check that it's not too salty before adding it).Cover and simmer over low heat for ten minutes. Taste and add salt to taste if you find it necessary (I did not).