In Amalfi, Italy, cooks making pesto forgo the classic fresh basil in favor of strips of zest from the local lemons, “sfusato amalfitano.” Combined with almonds, Parmesan and oil, it makes a bright, aromatic pesto perfect for tossing with pasta. In our version of the recipe, from our cookbook “ Milk Street 365: The All-Purpose Cookbook for Every Day of the Year ,” a little sugar is added to temper the acidity of the lemons and replicate the flavor of the larger, sweeter lemons on the Amalfi Coast.
For extra citrus complexity, we also add lemon zest to the pasta cooking water; the oils from the zest lightly perfume the spaghetti, reinforcing the lemony notes of the pesto. Instead of pounding the pesto with a mortar and pestle — as is classic with basil pesto — we use the food processor. The zest is removed from the lemons in large, thin strips, leaving the bitter white pith behind.
Half of the strips go into the pasta water, along with a little salt and sugar; the remainder are added to the bowl of the food processor, then pulsed with the almonds and cheese until the mixture resembles coarse sand. Olive oil then is added and processed until just incorporated. Cook the spaghetti in the lemon-scented pasta water until al dente, then combine with the pesto and some of the starchy pasta cooking water.
Toss, adding more pasta water as needed until it coats the noodles. Don’t forget to remove the lemon zest from the boiling water before dropping in the pasta. If left i.
