Pasta all’Amatriciana with Confit Tomatoes

Preheat oven to 300°F. Season drained tomatoes generously with salt and pepper. Place in a cast-iron skillet, Dutch oven, or baking dish that almost isn’t big enough to hold the tomatoes in a single layer. A little overlap is okay, since the tomatoes will shrink as they cook. A too-big vessel will force you to use more olive oil, and olive oil ain’t cheap.

Using a vegetable peeler, remove a few wide strips of zest from a lemon and twist them over the tomatoes to release a spritz of essential oils. Drop the zest into the tomatoes and save the lemon for squeezing the juice over later.

Add enough extra-virgin olive oil to just cover the tomatoes. Don’t use an extremely expensive, robustly flavored oil. A fairly mild, buttery and not-too-peppery type in the everyday category is better. Cover tightly with aluminum foil or a lid.

Bake until tomatoes are absolutely tender all the way through when pierced with a tester, checking after 2 hours.

Using a slotted spoon, transfer tomatoes to a storage container. Season with a squeeze of lemon and more salt and pepper as needed. Pour cooking liquid through a fine-mesh strainer set over a medium bowl. Pour strained cooking liquid over the tomatoes to cover (if you don't have enough, add more olive oil). Let cool, cover, and refrigerate up to 1 week.

Bring a large pot of salted water to a boil for pasta. Meanwhile, make the sauce.

Cut pancetta into 1 × 1/2-inch pieces and put in a Dutch oven, then place over medium-low heat. Cook, stirring occasionally, until about half the fat has rendered and edges are starting to turn golden brown and pieces are equal parts crisp and chewy, 8 to 10 minutes. Use a slotted spoon to transfer pancetta to a small plate and set aside. Reserve pot with drippings.

Add cooking liquid and oil from confit to pot, increase heat to medium, then stir in onion and season with salt and black pepper. Cook, stirring every couple of minutes, until onion is translucent and floppy, 6 to 8 minutes. Don’t rush this step; it’s essential for unlocking the onion’s sweetness. Increase heat to medium-high and cook until onion is golden brown, 3 to 4 minutes longer. Meanwhile, tear tomatoes into 1/2-inch thick pieces.

Add tomatoes and crushed red pepper flakes to pot and cook, stirring often, until tomatoes give up their juices and start to lightly caramelize. Stir pancetta back into sauce along with any accumulated juices, then taste and adjust seasoning with salt and black pepper. Remove from heat and cover pot until pasta is ready.

Add pasta to boiling water and set a timer for 2 to 3 minutes less than package instructions (it should be very al dente and will finish cooking in the sauce). Use tongs or a spider to transfer pasta directly to pot of sauce along with about 1/2 cup pasta water. Cook over medium high, stirring and tossing constantly with tongs and adding 1/4 cupfuls of pasta water as needed until pasta is al dente and coated in a glossy, luscious sauce, about 2 minutes. Serve topped with Parmesan and more crushed red pepper flakes, if you like.