Onions cut into thin half-rings. Grind in a blender until smooth canned tomatoes. Cut the slices of cod medium. Cut each prunes into three parts.
In a large skillet, heat the grapeseed oil, add the onion, fry six minutes. Pour the vinegar, fry for another half a minute. Then add water, tomato puree, bring mixture to a boil.
Pepper, salt cod to taste. Pour in sauce with rosemary and prunes, cover with lid, cook for another fifteen minutes.
Sprinkle the finished dish with olive oil, sprinkle with black pepper and submit to the table. Enjoy the meal!