Bring 2 inches of water to a boil in a large, deep skillet. Salt water.
Hold a spear of asparagus at each end, snap and use the natural breaking point as guide to trim the spears. Reserve stems for soup. Simmer spears in salted water for 3 minutes, drain and cool.
Wipe pan dray and return to stove over medium heat; melt butter. When butter foams, add shallot and lemon zest, stir 1-2 minutes, add asparagus and heat through. Douse with lemon juice and season with salt; serve.