This salad is a perennial favorite at parties and picnics. The delicious tahini dressing recipe makes more than you need, but it keeps for 3 weeks in the refrigerator. It's convenient to have the dressing on hand so that you can make this salad quickly with whatever vegetables and pasta you might have. For optimum flavor and texture, the salad is best eaten within 2 days.
Combine the dressing ingredients in a bowl and whisk to combine.
Toss the pasta with some of the dressing, then add the vegetables and herbs. Toss again, adding more dressing as needed to moisten the salad.
Garnish with sesame seeds, if using. If not serving within an hour of assembly, refrigerate until serving time. Refrigerate any extra dressing.