This recipe is credited to Faith Heller Willinger, noted expert in Italian cooking

1 lb         fresh asparagus, tough ends trimmed
1 tsp       finely-grated fresh lemon zest
1/4 C      extra-virgin olive oil
1 lb         penne or other pasta
1/2 C      grated Parmigano-Reggiano

Directions
Cut asparagus into 1-inch pieces, reserving tips separately. Cook asparagus stems in 5-6 quarts boiling water with 2 tablespoons salt until very tender, about 6-8 minutes. Transfer with slotted spoon to a colander, reserving cooking water in pot, and rinse under cold water. Drain asparagus well, and transfer to a food processor or blender.

Cook asparagus tips in same boiling water until just tender, 3-5 minutes. Transfer with slotted spoon to colander, reserving boiling water in pot, and rinse under cold water. Drain tips well.

Puree asparagus stems with zest, oil and 1/2 C asparagus cooking water. Transfer sauce to a 4-quart saucepan.

Cook pasta in boiling asparagus cooking water until it still offers considerable resistance to the tooth, about three fourths of the recommended cooking time. Reserve 2 cups cooking water and drain pasta.

Add pasta, asparagus tips and 1/2 cup reserved water to asparagus sauce and cook over high heat 3-5 minutes, stirring, until pasta is almost al dente and sauce coasts pasta. Add more cooking water, 1/4 cup at a time, until sauce coats pasta but is a little loose (the cheese will thicken it slightly). Stir in cheese, salt and pepper to taste, and stir until cheese melts. Serve immediately.