Peel, halve and core the melon and cucumber, then dice the flesh.
In the meantime, sauté the onion rings in the port wine in a small saucepan for three to four minutes.
Place the melons and cucumber in a suitable bowl, add the port wine onions without the liquid and mix.
Stir the vinegar with the olive oil, orange juice, three quarters of the tarragon, salt and pepper to make a dressing and pour over the lettuce. Arrange on plates, surround with the slices of ham and bring to the table sprinkled with the remaining tarragon.
Tip: You can let the dressed lettuce stand for a little while before serving.
Tip: It’s best to use your favorite ham – then your dish will taste twice as good!