Preheat oven to 425 degrees F. Heat 1 tablespoon oil in a large cast-iron skillet over medium heat. Add onion, bell pepper and 1/4 teaspoon salt. Cook, stirring frequently, until the pepper is soft and the onion is beginning to brown, about 10 minutes. Remove the pan from the heat. Carefully layer eggplant, zucchini (and/or summer squash) and tomatoes in an alternating shingle pattern over the pepper and onion. (They will overlap quite a bit.) If you have extra vegetable slices, save them for another use. Drizzle with 2 tablespoons oil and sprinkle with pepper and the remaining 1/4 teaspoon salt.Advertisement
Place the pan in the oven and bake until the vegetables are tender, about 1 hour. Drizzle vinegar and the remaining 1 tablespoon oil over the top and sprinkle with marjoram. Let cool for about 5 minutes before serving. Leftovers can be refrigerated for up to 4 days.
3 fat, 3 vegetable