Wash the broad beans well and put them in a bowl with plenty of cold water to soak for at least 12 hours. Take them out and rub them together, removing as many skins as you can. Boil them in a saucepan with plenty of water for 35-40 minutes, adding salt to the end. Strain and leave to cool.
In a salad bowl, mix them with the tomatoes, cucumber and onion. Sprinkle with garlic, parsley, lemon juice and olive oil.
Season with cumin, salt, pepper and serve.