Sautée the onion in a large non-stick pan, then, when the onion is golden, add the meat and brown it on all sides. If you have a Dutch oven pot, this is a great time to use it.
1 onion, 1 kg round or chuck beef, 5 tablespoons extra-virgin olive oil
Pour tomato puree, wine, salt, and a cup of water over the meat, then let it cook over low heat for about three hours, turning the meat about every half hour, and adding water if the sauce dries up too much. If you are in a hurry, you can speed up the cooking time of the meat by using a pressure cooker and increasing the liquids: just make sure there is always enough water to cover the meat.
24.5 oz tomato puree, 1 cup red wine, 1 tablespoon salt
When the beef is fall-apart tender, set it aside and let it come to room temperature before slicing into it.
Serve the stracotto hot, and don't forget to save a little sauce for pasta the next day, as the tradition requires.