A twist on the classic basil pesto, this spicy condiment is a great addition to sandwiches, pastas, or soups. Mature arugula will contribute more pungency than baby greens, so bunched arugula is your best bet if you're looking for an assertive flavor. If you happen to have an abundance of arugula, make a double or triple batch of this pesto and freeze it for up to 3 months. If you plan to use the pesto in small amounts, freeze the sauce in ice cube trays and then store the frozen cubes in a zipper bag.
Place the garlic, pine nuts, and salt in the bowl of a food processor and pulse to chop roughly. Add the arugula, lemon juice, and cheese, and purée until smooth. With the machine running, add the olive oil in a slow, steady stream. Taste and add more salt if desired.
Transfer the pesto to a clean container, cover, and store in the refrigerator for up to 1 week.