Make the dressing first. Take the small mixing bowl and mix together the vinegar, tarragon, mustard, fennel seed and olive oil. Whisk well so that the dressing has even taste when the ingredients blend together.
Prepare the vegetables now. Chop up the tarragon and watercress. Slice the fennel bulb and grind the fennel seed. Cut the tomatoes into thick wedges. Toss together all these in a large salad bowl so that they blend together well.
Spoon over the dressing and toss again so that the vinaigrette gets coated over the vegetables. Season with salt and freshly ground pepper according to your taste. The salad is ready to rock your meal. Do a taste check and serve right away.