Preheat the oven to 350°F. Drizzle a few drops of oil in each of four 4- to 6-ounce ramekins.
Arrange 4 or 5 slightly overlapping slices of yellow squash over the bottom of each mold. Cover with a layer of zucchini and sprinkle with a little oil, salt, pepper, and half the herbs. Add another layer of squash, seasonings, and herbs. Top with a final layer of tomatoes and sprinkle with oil, salt, and pepper. Be sure to season the squash and the final tomato layer well.
Place the molds on a baking sheet and bake until bubbly, 25 to 30 minutes. To serve, invert each tian onto a spatula, let the juices drain off, and then invert again from the spatula onto a serving dish.
For the fresh herbs, substitute all savory, all thyme, or 1 teaspoon herbes de provence.
For olive oil, substitute Rosemary Oil.
A tian is a shallow ramekin. Disposable 4½-inch aluminum pie tins are a good substitute.
If you have really flavorful zucchini and squash, you may omit the herbs altogether.