Wash the beef well, careful not to leave any pieces of bones in the meat. Pour the 12 cups of water in a pot and heat it up. Add the beef and cook on medium heat for about 1 hour and 20 minutes until the meat is cooked. In the beginning, remove all the foam that the meat releases with a skimmer (slotted spoon).
Add the potatoes in the soup, along with the carrot and celery. Cook for another 20 minutes. Add the rice (after washing it well to remove the starch, until the water is clear), the salt and pepper and stir. Add the remaining 2 glasses of water and cook for another 15 minutes for the rice to soften. Cover the soup, set it aside for ½ hour to “rest” and for the flavours to combine. Return it onto the heat until it warms up and add ¼ cups (60ml) lemon juice. Stir and serve the soup with cut lemons, for everyone to add as much as they like.