2 medium yellow onions, halved
2 medium green onions, halved
1/4 cup olive oil
1/4 cup white wine vinegar
salt and pepper to taste
1/8 teaspoon dried marjoram
Place fresh mushrooms and onion in a large glass dish. Season with salt and pepper.
Cover dish with lid of aluminum foil. Place salmon in foil and turn to coat with water. Pour or brush with olive oil. Refrigerate for 6 to 12 hours or overnight, or until fish is tender.
Heat olive oil in a medium skillet over medium-high heat. Saute mushrooms and onion in olive oil until fully cooked. Remove from skillet and drain on paper towels. Stir in vinegar and salt and pepper.
Return pepper to skillet and cook, stirring frequently, until all vegetables are heated and turn into a deep golden yellow color.