This omelet is called moissonière because it was eaten cold under the trees after the harvest (la moisson). It can also be served warm.
Peel the onions. With a sharp knife make an incision in each and put in a clove. Place the onions in a bowl of water, add the vinegar, and marinate them for half a day. Then dip them in boiling water for a few minutes and drain. Remove the cloves and slice the onions into thin slices.
© 1990 Mireille Johnston estate. All rights reserved.