1) Trim fennel and cut it into thin slices.
2) In boiling salted water, blanch fennel for 5 minutes.
3) Drain the fennel slices and keep aside.
4) Peel onion and cut into rings.
5) Cut the tomatoes into slices.
6) In a salad bowl, arrange fennel, onion and tomatoes in layers.
7) In another bowl, make dressing by mixing together oil, vinegar or lemon juice and seasoning.
8) Pour the dressing over salad.
9) Chill for 15 minutes.
10) Serve the chilled salad with your meals.