Cook the pasta until al dente, drain well and leave to cool in a bowl.
Peel the onions and cut into thin rings. Remove the stem and seeds from the peppers, dice into small pieces. Halve the zucchini lengthways and cut into thin slices. Eight the tomatoes and add all the vegetables to the pasta.
For the marinade, mix all the ingredients well, pour over the salad, mix well and let steep for about 1 hour.