Wash the tench and dab dry. Sprinkle with lemon juice, season with salt and pepper. Turn the fish in the flour. Fry in portions in hot fat on both sides for about 10 minutes and keep warm if necessary. Clean, wash and drain the salad. Wash cucumber and tomatoes and dab dry. Cut cucumber into slices and halve tomatoes.
Peel onion and cut into fine rings. Mix vinegar, salt and pepper. Whip oil into it. Mix salad ingredients and vinaigrette. Serve with the fish. Serve with parsley potatoes