Preparation:
First clean and chop the onions and add them to a saucepan over low heat with oil. Meanwhile, wash the anchovies under water to desalinate them and fillet them. Add the anchovies to the onions and let them slowly melt.
After the bigoli are cooked, add them to the sauce together with a couple of tablespoons of the cooking water (which you set aside earlier). Stir until the bigoli absorb the sauce well.