Peel the onions. Chop 1 onion finely. Wash, clean and chop the tomatoes. For the sauce mix vinegar and 1 tbsp. oil and season with sugar, salt and pepper. Mix sauce, onion cubes and tomatoes
Peel the garlic. Cut the remaining onions and garlic into fine cubes. Heat 1 tablespoon of oil in a pot and sauté the onion and garlic cubes until translucent. In the meantime, pour the beans into a sieve and rinse with water. Add the beans and stock to the pot, bring to the boil and puree finely with a hand blender. Season with salt and pepper and keep warm
Wash the parsley, shake dry, pluck the leaves from the stalks and, except for something to garnish, chop. Wash fish, dab dry and cut fillets into 12 pieces. Season with salt and pepper. Heat 1 tablespoon of oil in 2 pans. Fry the fish for about 2 minutes on the skin side first, then on the meat side for another 2 minutes. Arrange mashed potatoes, fish and tomato salad on plates. Sprinkle with parsley and garnish with lemon and parsley. Add the remaining tomato salad