Heat the olive oil until it’s shimmering but not smoking. Saute the the shallot, the guanciale and the pepper flakes until the onion is only lightly colored.
Turn down the heat to low and add the tomatoes. Simmer this while the pasta is cooking. Add salt and pepper.
When the pasta is cooked drain it saving a few tablespoons of pasta water (if needed). Add the drained pasta directly to the sauce and stir to combine. Make sure the sauce is “tight” but if it’s too tight flick in a little bit of the pasta water.
To plate: using tongs portion out the pasta on warm plates. Grate the pecorino cheese over each. If using the garnish sprinkle it over the top.