In the bowl of a food processor, blend arugula, basil, toasted walnuts, olive oil, garlic, lemon zest and juice, salt and a few grinds of pepper until well combined and smooth. Feel free to add extra olive oil if the pesto feels too thick or chunky.
Place a large pot of salted water over medium-high heat and bring to a boil. Add pasta and to cook to al dente. Drain and place back in pot. Fold in pesto. Serve hot in your favorite bowls with a generous sprinkling of Parmesan over the top of each bowl.