Preheat oven to 450F. Arrange fillets in 8x8x2 inch square baking dish. Saute onion and garlic in oil in medium size skillet over medium heat 3-5 minutes or until lightly softened. Add tomatoes, capers, basil, olives, lemon juice, oregano, salt if using and pepper. Simmer, stirring occasionally, 8 minutes. Spoon sauce over fish. Bake in preheated 450F oven for 10 minutes or until cooked through.
