Peel some very small baby vegetable marrows, only a few inches long, or cut some medium-sized ones into slices.
Cook in a pan on a moderate heat, with a little oil, add some chopped onion and parsley, salt, and a very little water; cover and simmer until the marrows are tender.
By then there should be no liquid left.
Arrange in a hors-d'oeuvre dish, and cover with slices of lemon from which pips and skin have been removed.
Serve very cold.