Place your fish fillets in a non heated large non-stick pan. Cover with lemon juice, water, onion, salt and pepper.
Place over high heat and bring to a simmer. Cover your pan loosely with a plate or pizza pan, lower heat and simmer for 5-8 minutes, depending on size of your fillets. The fillets will become completely opaque when cooked.
Make the Salsa
While the fillets are simmering away, chop your tomatoes, olives, onions and fresh basil and add to a medium mixing bowl.
Add lime juice, salt and pepper and gently toss until evenly distributed. Set aside.
Plating
When fish is ready, transfer the fillets to serving plates and top with tomato salsa.
Garnish with fresh basil leaves and serve immediately with a side of greens.