Cook pasta according to package and save about 100 ml of the pasta water for the sauce later.
Cut asparagus in smaller pieces (about 3cm long).
Zest and juice the lemon.
Steam asparagus pieces for 3 minutes.
Melt butter and olive oil in large pot.
Add lemon zest and juice, and heavy cream.
Let cook together for five minutes.
In the mean time shred Parmesan cheese, and add to pot. Let the cheese slowly melt while stirring.
Add pasta water if the sauce seems to thick.
Taste with salt and pepper.
Add steamed asparagus and mix with the sauce.
Add in tagliatelle and stir to make sure the sauce covers all pasta.
Plate the pasta and serve with a wedge of lemon.