In a bowl add the sliced red onions and 1/4 cup rice wine vinegar or enough to cover. Set aside to marinate for 30 minutes or overnight.
In a mixing bowl add the mayonnaise, rice wine vinegar, honey, mustard, tarragon, salt and pepper, whisk thoroughly.
Chop the broccoli into florets and trim and chop the stalks as well if you like into bite size pieces. Place in a mixing bowl and add the marinated red onions, pepitas and golden raisins.
Pour the dressing over the salad and mix to completely coat the vegetables and chill for 20 minutes prior to serving.