Peel the asparagus bases with a swivel peeler and trim the woody ends. Blanch in boiling salted water for 1½-2 mins until just tender. Drain and refresh under cold running water.
Trim the base of the lettuce leaves and arrange on a large shallow bowl or platter. Scatter over the asparagus spears and red onion, season well and drizzle with vinaigrette just before serving.
Gordon's know-howHere’s my quick way to prepare asparagus. Simply bend each spear and snap where you feel it naturally give, breaking off the woody end.