Grilled Tuna with Red Wine, Caper, and Olive Sauce

I first tasted this dish (or one very nearly like it) on the end of a barely inhabited island located a few miles off the Côte d’Azur. The Ile de Porquerolles is where to go to escape the crowds and traffic of the Riviera. Immortalized by the mystery writer Georges Simenon, the island has a single town you can cross on foot in about ten minutes, set amid acres of national parkland. The residents had the good sense to ban cars from the mainland.

But in France nowhere is so remote tha