Heat oil in large frying pan over medium heat. Add onion and cook for 4 minutes until tender. Add garlic and saute until fragrant, about 1 minute. Pour in tomatoes, tomato paste and paprika and cover and simmer for 15 minutes. Add olives, nuts, capers and fish and cover and simmer 20 minutes or until fish is opaque and beginning to flake when tested. Serve hot.