Bring a large pan of water to a boil, add the asparagus and cook 30 seconds to 2 minutes (until crisp tender), depending on the size of the asparagus. Immediately plunge cooked asparagus into ice water, drain and pat dry. Refrigerate until serving. Combine all of the dressing ingredients and whisk until thoroughly combined. Divide lettuce leaves among 6 plates. Fan 1/6 of the asparagus and melon wedges over the bed of lettuce. Top with crabmeat. Drizzle with dressing and serve immediately.