Bee Wilson searches for the perfect salad nicoise

The <em>sine qua non </em>of a salade nicoise is not fish, but tomatoes

Ah, salade nicoise, the taste of summer: so easy to eat, so trouble-free to make. Just take a tin of tuna, add cooked French beans and tiny new potatoes, strew generously with anchovies, add olives and assorted pep la - and now you have just the thing for supper in the garden, an authentic taste of Nice, no?

Well, actually, no. Half the things that it would first occur to a foreigner to put in a salade nicoise are, to the native eye, quite wrong. Green beans or any other cooked vegetable have no place here. The same goes, doubly so, for boiled potatoes, however small they are. It is also quite mistaken to think that tuna is the indispensable ingredient.

Jacques Medecin, a former mayor of Nice, is well qualified to comment on the true components of this dish, as he does in the new edition of his delightful cookbook, Cuisine Nicoise (just out from Grub Street, £12.99).

Nice is a city not unacquainted with corruption; perhaps all the more reason for it to keep its salads pure. Medecin laments that "salade nicoise is one of those dishes that is constantly traduced. At its most basic - and genuine - it is made predominantly of tomatoes, consists exclusively of raw ingredients (apart from hard-boiled eggs) and has no vinaigrette dressing: the tomatoes are salted three times and moistened with olive oil."

Traditionally, it should include salted anchovies or tuna, never both (anchovies used to be seen as an economical surrogate for expensive tuna). It may also include peeled and sliced cucumber, thinly sliced green peppers, spring onions, a little garlic, black olives, chopped basil, salt and pepper. If you want to push the boat out, Medecin rather reprovingly suggests that you add some small broad beans or artichoke hearts, your choice to be made "depending on the time of year, either one OR the other OR neither but not both".

However, Medecin admits that even the Nicois do not obey all of these rules any more, and often - the horror! - "combine anchovies and tunny fish in the same salad".

That messiah of the simple, Escoffier, also included both tuna and anchovies in his salade nicoise, though nothing else except tarragon, chervils, chives, mustard and oil. Even Elizabeth David, usually a purist in these matters, suggests adding tuna and cooked beetroot or potatoes, depending on taste and "what is to come afterwards".

Really, it is a compliment to salade nicoise rather than a betrayal that it has been so messed around with. Even if they are not truly Nicois, many of the tuna and green-bean variants inspired by the original are utterly delectable, though substituting salmon, as some suggest, is really a step too far. Alice Waters makes her salade nicoise with copious fresh tuna, yellow and red tomatoes, yellow and green beans, and whole cupfuls of green herbs.

Ruth Watson gives a far simpler idea for a salade composee of tuna, shallots and green beans. Alastair Little, meanwhile, makes a moreish dressing to go with salade nicoise that would plunge Monsieur Medecin into despair - a kind of tangy, mayonnaisey sauce including garlic, Worcester Sauce and even ketchup. This is so far from the original, that it is no longer inauthentic, but sui generis.

If it gives you pleasure, why shouldn't you sear a fresh tuna steak and serve it with a salad of green beans, capers, roasted red peppers, tomatoes and flat-leaf parsley, mixed with anchovies, potatoes and anything else that takes your fancy? Just don't take the good name of the city of Nice in vain as you do so.