Step 1Snap or cut off the tough ends of the asparagus spears. If the asparagus spears are thick, use a vegetable peeler to peel the lower 2/3 of the stalk. Place the asparagus in a steamer basket over boiling water. Cover and steam until the spears are tender when pierced with the tip of a knife, 10 to 15 minutes.
Step 2Place the sesame seeds in a small skillet and toast over medium-low heat until they turn light brown and become aromatic, 1 minute. Watch carefully; they tend to brown quickly. Crush the seeds with a mortar and pestle.
Step 3Combine the seeds with the soy sauce, mirin, sugar and lemon juice. Arrange the asparagus on a platter and pour the sesame sauce over the top.