For the couscous salad, salt the water and prepare couscous in it. Cut onions into rings and chop tomatoes, peppers, cucumber and celery.
Heat oil in a pan and fry onion rings in it, then add the rest of the vegetables and fry them briefly as well. Add couscous and mix with vegetables.
Season with lemon juice and salt and garnish the couscous salad with basil leaves when serving.