[momania]

Opinions differ here. It's said that onions were added to deflect the salty taste, as much salt was used in the old days for preservation. As we now have deep freezers and shipments on ice, there is no or less salt used, so no need for onions. I've also heard stories that onions where added to deflect the smell and taste of old herring in the olden days.

Some people still like it with onions though, but I'd prefer without (and also without pickle)