extra-virgin olive oil or lard, as per taste but consider a thick layer in the pan
3 thick slices of guanciale, pancetta, or good bacon cut into stripes or cubes
1 red onion, roughly cut
2 cups Basic Tomato Sauce
Freshly grated Pecorino Romano
In a saute pan, combine the olive oil, with the onion, cook the onion at low heat (otherwise it burns) and once cooked remove it from the pan.
Add the guanciale and cook until the guanciale has rendered much of its fat, about 12 minutes. Remove the Guanciale (you want it to be crunchy, right?)
Add the tomato sauce, turn up the heat, and bring to a boil, then lower the heat to a simmer and allow to bubble for HOURS!!! The longer it cooks the tastier it gets. If you were thrifty with your oil you’ll notice that the sauce will tend to stick to the pan after a while, if you were generous the oil will allow you a much longer cooking time, you’ll notice a layer of fat atop the cooking sauce. When the sauce turns to deep red and you like the taste of it you can remove it from the heat. Don’t be in a hurry, it needs its time. Do not add any extra salt as the guanciale will provide enough saltiness.
When you think it is almost time to serve, or maybe you can prepare the sauce the day before (even tastier) Bring a large pot of water to a boil and add thick salt to taste (water should have the saltyness you desire in your pasta, so taste it before adding too much salt).
When the water boils (a lot, not only a few random bubbles) cook the pasta (if freshly made, i twill be ready once it floats, if dry, check the cooking time and cook it a minute or two less than the package directions, until still very firm; drain.
Heat up the sauce (if cold) and heat up the guanciale (separatly). Add the pasta to the simmering sauce and toss for about 1 minute to coat.
Divide the pasta among four heated bowls and serve immediately sprinkling the hot guanciale and top with freshly grated pecorino cheese.