A Summery Gratin Worth Turning On the Oven For

My brother-in-law Tim arrived Friday evening with his four children, a case of beer, and a bag of vegetables—the fruits of his, as he described, “backyard CSA”: a half dozen plump, weighty Cherokee Purple tomatoes, two dirt-shrouded onions with straggly greens intact, and four one-pound-plus summer squash clubs. Um, thanks? At the moment, it was hard to say who should be thanking who.

It turns out, I would be thanking Tim. His children, moments after their arrival, disappeared, swallowing mine in their wake. The beer, shortly thereafter, went down easy, dissolving (briefly) all the worries in the world. The tomatoes, the next day, floated atop cream cheese-smeared bagels. The squash, two days later, baked into this gratin, one of my favorite summer meals.

As you can gather, I had my doubts about the squash—a pass down the mandoline revealed airy centers and a host of big, uninviting seeds. After a brief roasting, however, my concerns faded. The golden slices tasted sweet without a trace of bitterness.

Over the years, I’ve made many variations of this gratin—it’s simple: roasted vegetables + grated parmesan cheese + red bell pepper-tomato sauce + fresh bread crumb topping. It’s a foolproof formula. A simple green salad is all it needs.

Note: This is not a weeknight meal. If you roast many pounds of vegetables, you will need many sheet pans. To make the sauce, you need a pot. If you, as I, like grinding bread for crumbs and blocks of cheese in a food processor, count on dirtying that, too. That said, this dish will comfortably feed six people, and it’s an answer to the question asked often this time of year: What to do with all this darn squash? If you dedicate time to this gratin, you’ll no longer spend time conducting stealth missions, dropping cases of zucchini on neighbors’ doorsteps or into strangers’ unlocked cars. Gather your burdensome, seedy, home-grown baseball bats. They’re all welcome here.

Roasted vegetables: I’ve used eggplant, zucchini, summer squash and a mix of all three though I imagine any number of vegetables would work well here. The key is in the roasting, which draws out the moisture of the vegetables, ensuring the flavor of the gratin will be sweet and concentrated, and the texture, not watery. You can roast as many or as little vegetables as you wish. I used a 9x13-inch baking dish here, but in the past, when I’ve roasted fewer vegetables, I’ve used an 8- or 9-inch square or circle baking dish.

Red-pepper tomato sauce: This is an old Michael Chiarello recipe from The Tra Vigne Cookbook, and it’s one of my all-time favorite sauces to make, this time of year especially: Throw chopped tomatoes and red peppers (about 2 cups each) into a pot with water and salt—no oil or butter (yet). Simmer until the liquid nearly evaporates and the vegetables thicken, then purée them with basil and butter or olive oil. Toss the sauce with pasta, serve it as a dip, or layer it, as here, with vegetables (or noodles). It’s so good.

Grated Parmesan: For quick grating, use the shredder attachment of your food processor. Then, before cleaning it, use the main blade to grind the bread for the topping.

Bread crumb topping: Here, the fresh bread crumbs are tossed simply with olive oil, salt, and grated parmesan, but you could season them further with herbs such as thyme or parsley or with minced garlic or, for a kick, crushed red pepper flakes. The fresh crumbs bake into a golden layer, melding into the roasted vegetables beneath them. This same mix can be spread over pasta, beans, meat, other vegetables—it’s irresistible.

What do you like to put in your gratin? Let us know in the comments!