I love mackerel and eat it often. Because of it's oiliness, it goes very well with vinegar and soy sauce. This was fabulous way to serve mackerel and the salsa was a perfect match to the strong taste of mackerel. The idea of making salsa with mostly onion is an interesting one, but when combined with toasted saffron, wine vinegar, olive oil, and chopped green grapes, it becomes sublime! Totally good eating. Thank you for posting this recipe. Made for ZWT 5.