There is no one absolute recipe for tapenade, the Provençal olive spread, and the ratio of one ingredient to another varies according to taste. The capers are usual but not obligatory. The best olives for this relish are the black Greek ones you can buy salted in jars. Cover these with extra-virgin olive oil and leave at room temperature for one month. After this time, much of the salt will have been extracted, while the olives absorb the oil and plump up to a delightful succulence.