Oven-Roasted Ratatouille

Adapted from David Tanis, Saveur Magazine 2016

Makes about 3 - 4 cups, depending on the size of the vegetables

3 tablespoons extra-virgin olive oil plus additional for the pan and drizzling atop
1 large white onion cut into 1/4-inch slices
1 teaspoon fresh thyme chopped
1 teaspoon fresh marjoram chopped
4 cloves fresh garlic minced
1/4 teaspoon crushed chile flakes to taste
3/4 pound zucchini about 4 medium, cut into 1/4-inch thick slices
3/4 pound firm eggplant about 1 small, cut into 1/4-inch thick slices
3/4 pound ripe tomatoes about 3 medium, cored and cut into 1/4-inch thick slices
Fresh basil leaves to garnish
Sea salt and freshly ground black pepper to taste

Lightly oil bottom and sides of a 2-quart baking dish, preferably ceramic.
Using a 10-inch skillet/fry pan, place 3 tablespoons of olive oil and spread to evenly coat the bottom of the pan. Add the sliced onions with salt and pepper to taste. Cook until onions are softened and translucent, then add thyme, marjoram, and garlic. Continue cooking a few minutes until garlic softens but doesn't begin to brown. Transfer to the prepared baking dish, spreading evenly, and set aside.
Meanwhile position an oven rack to the lower third of the oven and preheat to 400°F. Atop the onion layer, arrange the zucchini, eggplant, and tomatoes in alternating rows with sliced vegetables stacked vertically on edge and slightly overlapping. You want to see the colorful skins on each row for the visual impact of the finished dish.
Pack the rows together tightly and continue until the dish is filled. Season the vegetables with additional salt and pepper to taste, and drizzle another tablespoon or so of olive oil.
Bake for 15 minutes, uncovered, at 400°F, then reduce the oven temperature to 350°F and bake until the vegetables are tender, about 45 - 60 minutes. Baking time will depend on how tightly the vegetables are packed. The vegetables will continue cooking with carry-over heat from the baking dish.
Remove the dish from the oven and cool to room temperature. This allows for the flavors to develop further. Garnish with a flourish of fresh torn basil before serving.