Step 1

Bring salted water to a boil, add pasta, and cook according to the package instructions, 8-10 minutes.

Step 2

While the pasta is cooking, combine spinach, basil, olive oil, walnuts, Parmesan, and salt in a food processor or blender. Blend until the mixture is well blended, pausing to scrape down the sides as necessary. If you prefer a chunkier pesto, stop processing while it still has some texture.

Step 3

Taste, and adjust salt if necessary. If you feel it lacks zing, add a squeeze of lemon juice or some grated lemon zest.

Step 4

Drain pasta, but reserve some of the pasta water. Toss pasta with the pesto and add some of the pasta water, if needed. Serve with grated Parmesan cheese.