Chop onions. Wash rhubarb and cut into slices 3 centimeters. Boil the broth and simmer the fish in it under the lid on low heat for about 5 minutes. For the sauce, pass in vegetable oil onion, add the rhubarb, red wine and sugar and cook for 4 minutes. Postpone 3 tablespoons of rhubarb. Add to the sauce mustard and fine grated ginger root. Mash into puree sauce with blender, add the rhubarb, warm and fed to the fish.