Step 1

Heat the olive oil in a large (preferably, straight-sided) skillet over medium heat. Add the diced pancetta and cook, stirring frequently, until most of the fat has rendered into the pan and the pancetta is crispy and caramelized slightly. Using a slotted spoon, remove the crispy pancetta and place in a seperate small bowl, leaving any fat behind in the pan.

Step 2

Over medium-low heat, add the diced onion and sauté in the rendered fat for 3 to 5 minutes, stirring frequently, until the onions are soft and lightly caramelized. Add the garlic and continue to sauté for an additional 2 to 3 minutes, being careful to avoid burning the garlic or onion. If needed, deglaze the pan with a tablespoon of water to scrape any bits of crispy pancetta or bits from the bottom of the pan.

Step 3

Add the tomato paste and 1 to 2 teaspoons dried red pepper flakes (if you are unsure, use the smaller quantity and increase to taste), and continue to cook, stirring frequently, over medium heat for 1 to 2 minutes, or until the paste has thickened slightly.

Step 4

Add the pancetta and any extra rendered fat back into the skillet, along with the crushed tomatoes. Bring the sauce to a low simmer, and cook, stirring every few minutes, for 15 to 20 minutes. The sauce should be relatively thick. Add the grated cheese to the sauce and season to taste with salt and pepper. Place over low heat while you cook the pasta.

Step 5

Meanwhile, bring a large pot of salted water to boil. Add the pasta and cook until al dente. Reserve 1 cup (240 mL) of the starchy pasta cooking water and drain the pasta. Return the drained pasta back into the pot, toss with a tablespoon of unsalted butter, and add the sauce, adding pasta water as necessary until the pasta and sauce are well incorporated. Serve pasta with extra grated parmigiano-reggiano cheese on the side.