Combine the cabbage, Spanish onion, capers, olives, tomatoes, cucumbers and red capsicum together and set aside.
In a food processor blend the basil, rocket, lime juice, mirin and garlic together with olive oil until smooth and runny.
Brush the fish with olive oil and sear for 3 - 4 minutes each side.
Serve the fish on top of the rainbow salad and top with rocket salsa.
Note: If you're making this dish for just 2 people, make the same quantity of salad and take it for lunch the next day.