Step 1

Quarter 1 medium leek lengthwise. Cut the white parts crosswise into 1/2-inch pieces (about 3/4 packed cup). Halve 1 small fennel bulb. Dice 1 half, then very thinly slice the other half. Halve 8 ounces cherry tomatoes. Halve 1 Thai red chile lengthwise (do not remove the seeds). Coarsely chop 3 tablespoons fresh parsley leaves. Cut 3 1/2 ounces guanciale or pancetta into thin matchsticks if using.

Step 2

Bring a large pot of heavily salted water to a boil over medium-high heat. Meanwhile, cook the guanciale and vegetables.

Step 3

Heat 1 tablespoon of the olive oil in a large skillet over low heat until shimmering. Add the guanciale and cook, stirring occasionally, until golden brown, about 5 minutes.Using a slotted spoon, transfer the guanciale to a plate. Cover to keep warm.

Step 4

Add 1 tablespoon of the olive oil to the pan. Add the leek, chopped fennel, chile, and a large pinch of kosher salt. Increase the heat to medium and cook until the fennel and leeks are very soft but not browned, stirring occasionally, about 5 minutes. Remove and discard the chile.

Step 5

Add the remaining 1 tablespoon olive oil, tomatoes, and a large pinch of kosher salt to the pan. Cook, stirring occasionally, until the tomatoes have broken down and are mostly soft, 7 to 8 minutes. Meanwhile, add 12 ounces dried rigatoni to the pot of boiling water and cook according to package directions until al dente.

Step 6

Add the thinly sliced fennel to the sauce and cook for 3 minutes. If the pasta is not ready yet, remove the pan of sauce from the heat.

Step 7

Reserve 1/2 cup of the pasta cooking water, then drain the pasta. Add the pasta to the sauce and toss to combine over low heat. If you prefer the pasta to be a bit saucier, add the reserved pasta water a tablespoon at a time until it reaches the desired consistency. Remove from the heat, add 1/2 cup grated Parmesan cheese, and toss to combine. Transfer to a serving bowl and sprinkle the parsley and guanciale on top. Serve immediately.