Oregano-Baked Tuna With Tomatoes and Golden-Brown Potatoes

This is a typically Greek, Turkish or Sephardic way of preparing tuna. The sauce is zesty, and permeates the hearty fish. In the Mediterranean, September is often the month when fishermen land their biggest catches of tuna, and it is also the time when the local women are hard at work preparing this dish. On Alonnisos, one of the Greek Sporades Islands in the Aegean Sea, it is traditional to cook the dish in the ovens of the local baker, after the final bread of the morning has been baked.