- Cut the asparagus into 1/2 inch slices on the diagonal, or just into 3 pieces.
- In a steamer set over boiling water steam asparagus, covered, until crisp-tender, about 3 minutes.Drain and rinse under cold water to stop cooking. set aside.
- In a 6-quart kettle bring 5 quarts salted water to a boil for pasta.
- In a deep 12-inch skillet heat butter and cream over moderately low heat until butter is melted and stir in zest, lemon juice, and salt. Remove skillet from heat and keep sauce warm, covered.
- Add pasta to boiling water and boil, stirring occasionally, until al dente. Ladle 1/4 cup pasta water into sauce and drain pasta in colander.
- Immediately add pasta and asparagus to sauce and cook over moderate heat, tossing, 1 minute, or until heated through. Add basil and salt and pepper to taste and toss well.
- Sprinkle pasta with a little Parmesan and serve more Parmesan on the side.