Wash the asparagus, trim the woody ends, and chop into bite-sized pieces.
Bring a large pot of salted water to a boil and cook the spaghetti according to package instructions. Reserve a cup of pasta water and drain.
Melt the butter in a large skillet over medium heat and sauté the chopped asparagus for about five minutes until bright green and tender.
Add lemon zest to the skillet and stir to infuse the dish with a bright aroma.
In the empty pot, melt the crème fraîche over low heat. Add reserved pasta water to create a creamy sauce and stir in more lemon zest and black pepper.
Combine the drained pasta with the creamy sauce, adjusting the thickness with more pasta water if necessary.
Squeeze lemon juice over the sautéed asparagus and mix it into the pasta.
Plate the pasta, topping it with remaining asparagus, extra lemon zest, Parmesan cheese, and black pepper.
Notes
Store leftovers in an airtight container in the refrigerator for up to three days.