Wash, peel, and dice the tomatoes into small cubes (5 to 8 millimeters), making sure to keep the juice.Add them to the couscous in the bowl.
Wash and peel the cucumber, then dice it into small cubes as well.Add it to the couscous in the bowl.
Wash and thinly slice the spring onion. Wash and finely chop the fresh herbs (mint, cilantro, and flat-leaf parsley), then add everything to the bowl with the couscous and vegetables.
Add the juice of half a lemon and 2 tablespoons of olive oil.Season with salt and pepper, and mix well.
Cover and refrigerate for at least an hour, or even overnight.Just before serving, adjust the seasoning by adding a little more lemon juice, olive oil, salt, and pepper if needed.Mix and serve.
Notes
If you use bulgur instead of semolina, you will need to let it soak and swell overnight.