1. Slice onions into thin rings and then in half.
2. Place separated half rings in bowl and pour boiling water over them. Let sit 3 to 5 minutes, then drain.
3. Cut cucumbers (with ruffle cutter if possible) into thin slices and add to onions.
4. In a separate bowl, combine remaining ingredients, except parsley, mixing well. Pour dressing over onions and cucumbers, then toss. Top with parsley and chill several hours or overnight before serving.