• 20 ripe medium plum tomatoes (3 to 3 1/2 pounds)
• 1/3 cup extra-virgin olive oil, plus more to finish the dish
• Pinch of crushed red pepper flakes
• Kosher salt and freshly ground black pepper
• 1 pound spaghetti, either high-quality dry or homemade
• 1 tablespoon unsalted butter
• 6 to 8 fresh basil leaves, well-washed and dried, stacked and rolled into a cylinder and cut thinly crosswise into a chiffonade
• 1 ounce (about 1/2 cup) Parmigiano-Reggiano, freshly grated, plus extra cheese if desired
1. To peel the tomatoes, bring 3 to 4 quarts of water to a boil. Have a large bowl of ice water nearby. Cut a small X on the bottom of each tomato. Ease about 5 tomatoes into the pot. Cook for about 15 seconds, then scoop them out and put them in the ice water. Repeat with remaining tomatoes.
2. Using the tip of a paring knife, pull off the tomato skin starting at the X. If the skin sticks, try a vegetable peeler using a gentle sawing motion. Cut the tomatoes in half through the equator, and use your finger to flick out the seeds.
3. In a wide pan such as a 12-inch sauté pan, put 1/3 cup olive oil over medium to medium-high heat. Add the tomatoes and red pepper flakes, and season lightly with salt and pepper. (As the tomatoes reduce, the salt becomes concentrated.) Cook the tomatoes for a few minutes to soften.
4. Using a potato masher, crush the tomatoes finely. Cook for 20 to 25 minutes, until the tomatoes are tender and the sauce has thickened. (Stir frequently and lower the heat if needed to prevent burning.. There should be about 3 cups. (If not using right away, refrigerate for up to 2 days. Freeze for longer storage.)
5. Cook the spaghetti in an ample amount, at least 4 quarts, of well-salted (about a tablespoon) water until just shy of al dente. Drain, reserving a cup of the pasta cooking water.
6. Add the pasta to the pot with the sauce. Cook over medium to medium-high heat, gently and continually tossing with wooden spoons and shaking the pan as needed until the pasta is just tender and incorporated into a cohesive-looking sauce. If the sauce seems too thick, add a little of the pasta cooking liquid.
7. Remove the pan from the heat and toss the butter, basil and cheese with the pasta, which should take on an orange hue. Serve immediately, with extra cheese if desired. Serves 4.