This may be my favorite summer vegetable dish. It effortlessly combines the most delicious bounty of the season and it tastes divine to boot. The addition of caramelized onions on the bottom is a stroke of pure genius. This is great served with any robust meat dish, and can be played around with by adding different sorts of herbs or cheeses. Multicolored fresh heirloom tomatoes are another distinctive addition. It is gorgeous on the table and is an easy knock-out when trying to impress the picky.
I suspect it would be quite pleasing with goat cheese on top as well. If you are in possession of a decent oven, the stated 60 minutes cooking time is a little excessive - keep an eye on it and pull it at 40 if it is bubbly delicious looking enough for your needs.
(Yes, I make this a lot).
Created by Susie Middleton.
For the onions:
2 Tbs. olive oil
2 medium onions (14 oz. total), thinly sliced
2 cloves garlic, minced
To assemble the gratin:
1-1/4 lb. ripe red tomatoes, cored and cut into 1/4-inch slices
3/4 lb. (about 2 small) zucchini or other green summer squash, cut into 1/4-inch slices on the bias
3/4 lb. (about 2 small) yellow summer squash or golden zucchini, cut into 1/4-inch slices on the bias
3 Tbs. olive oil
1/4 cup fresh thyme leaves
1 tsp. coarse salt
1-1/4 cups freshly grated parmigiano reggiano
Freshly ground black pepper to taste
To cook the onions: In a medium skillet, heat the olive oil over medium heat. Add the onions and sauté, stirring frequently, until limp and golden brown, about 20 min. Reduce the heat to medium-low if they're browning too quickly. Add the garlic and sauté until soft and fragrant, 1 to 2 min. Spread the onions and garlic evenly in the bottom of an oiled 2-qt. shallow gratin dish (preferably oval). Let cool.
To assemble the gratin: Heat the oven to 375°F. Put the tomato slices on a shallow plate to drain for a few minutes and then discard the collected juices. In a medium bowl, toss the zucchini and squash slices with 1-1/2 Tbs. of the olive oil, 2 Tbs. of the thyme, and 1/2 tsp. of the salt. Reserve half of the cheese for the top of the gratin. Sprinkle 1 Tbs. of the thyme over the onions in the gratin. Starting at one end of the baking dish, lay a row of slightly overlapping tomato slices across the width of the dish and sprinkle with a little of the cheese. Next, lay a row of zucchini, overlapping the tomatoes by two-thirds, and sprinkle with cheese. Repeat with a row of squash, and then repeat rows, sprinkling each with cheese, until the gratin is full.
Season lightly with pepper and the remaining 1/2 tsp. salt. Drizzle the remaining 1-1/2 Tbs. olive oil over all. Combine the reserved cheese with the remaining 1 Tbs. thyme and sprinkle this over the whole gratin. Cook until well-browned all over and the juices have bubbled for a while and reduced considerably, 65 to 70 min. Let cool for at least 15 min. before serving.
From Fine Cooking 33, pp. 24-29
June 1, 1999