Drain herring, discard sauce, reserve onions and cut herring pieces into quarters.
Combine all dressing ingredients and set aside.
Toss all salad ingredients, including reserved onions, in a large bowl.
Serve salad with dressing on the side, allowing guests to drizzle on dressing as desired. Garnish with fresh dill weed, if available. If preparing ahead of time, cover and refrigerate salad and dressing separately.