Peel and finely chop the onion. Wash the tomatoes and grate them dry. Quarter them, remove seeds and cut the flesh into fine cubes. Drain the pepper and let it drain. Wash the orange and grate dry.
Peel the skin in fine strips. Halve the orange and squeeze the juice. Wash fish fillets and dab dry. Season with salt and turn in flour. Heat olive oil in a pan and fry the fillets on both sides until golden brown. Remove the fillets and keep warm. Put onion in hot frying fat and sauté. Deglaze with orange juice. Add tomato cubes and pepper and simmer for 2 minutes. In the meantime wash basil and shake dry.
Remove the fillets and keep warm. Put onion in hot frying fat and sauté. Deglaze with orange juice. Add tomato cubes and pepper and simmer for 2 minutes. In the meantime wash basil and shake dry. Arrange fish and tomato sauce and sprinkle with basil and orange peel. Serve with mashed potatoes