Mix the mayonnaise, shallots, tarragon, capers, mustard, and garlic in a medium bowl. Fold in the crabmeat and season with 1/4 teaspoon salt and 1/8 teaspoon pepper.
In another bowl, toss the asparagus and onion with the olive oil and vinegar and season with the remaining 1/4 teaspoon salt and 1/8 teaspoon pepper.
Place equal amounts of the asparagus in the centers of four salad plates. Arrange the crabmeat salad over the asparagus. Lay three zucchini blossoms over each portion of crabmeat and garnish with the parsley.
Yield: 4 servings