For the yoghurt cream, rinse anchovies, dab dry. Chop anchovies and capers finely. Mix yoghurt, vinegar, mustard, anchovies and capers. Season with salt, pepper and 1 pinch of sugar.
Clean the salad, wash and shake dry. Wash and slice the tomatoes. Cut baguette into four pieces, cut each piece in half crosswise.
Rinse fish, dab dry and cut into 4 equal pieces. Season with salt. Turn in flour, shake off excess flour. Heat oil in a large frying pan. Fry the fish in it for about 3 minutes on each side until crispy.
Spread all bread halves with some yoghurt cream. Cover the lower halves with salad, fish and tomatoes. Season with salt and pepper, drizzle with remaining cream. Cover with the upper bread halves and serve immediately.