Wash the fish and cut into small pieces. Sprinkle with lemon juice and season with salt and pepper. Peel and wash carrot and celery. Cut carrots into slices and celery into thin sticks. Peel and finely chop the onion. Steam vegetables in hot fat for about 5 minutes. Add tomato paste.
Dust with flour. Add stock and wine while stirring constantly and bring to the boil. Season with salt and pepper. Add semolina. Let the fish simmer for about 5 minutes. Season soup again and serve sprinkled with chopped parsley