Make the dressing: blend miso, honey, mustard, onion powder, salt, vinegar, lemon zest, lemon juice, and aquafaba in a blender on medium-high for 10 seconds.
With the blender running, slowly stream in the oil to emulsify. Once incorporated, add poppy seeds and pulse once or twice to distribute. Refrigerate until ready to use.
Arrange iceberg wedges on a platter or individual plates. Spoon a generous amount of dressing over the wedges.
Scatter radishes, scallions, and parsley over the top and serve immediately.