Prepare Asparagus: Trim the woody ends off the asparagus.
Preheat Sous Vide Cooker: Preheat your sous vide cooker to 185°F (85°C).
Season Asparagus: Place the asparagus in a sous vide bag.Add butter. Seal the bag using a vacuum sealer or the water displacement method.
Cook Asparagus: Submerge the bag in the water bath and cook for 30 minutes.
Finish and Serve: Remove the asparagus from the bag. Before serving, season with salt and pepper, lemon zest. Top with freshly grated parmesan cheese before serving.