Thinly slice the red onion into slivers. Place in a bowl of cool water while you prepare the salad, then drain before using (this helps to mellow the flavor).
Thinly slice the radishes.
Clean and dry the spring greens. Place the greens in serving bowl.
Top with al dente asparagus, red onion, radishes feta crumbles and lemon zest.
Drizzle with Dijon Vinaigrette and serve.