As it turned out, San Marzanos were particularly suited for cooking, their flavor intensifying in the heat. These days, I consider myself something of a tomato specialist in California, where I live, always searching for the best varietals to plant in the right places. Still, I feel humbled whenever I recall that trip to Italy, a country that has a centuries-old tradition of seed sorting. A few stalls over in that same market, I came upon some datterini tomatoes. Similar to the San Marzano in appearance, these didn't require any heat to bring out their sweetness. I enjoyed them sliced with a little fresh mozzarella, everything drizzled with green, fruity olive oil, and topped with a pinch of crispy sea salt. That's it.