In a sauté pan, add 4 tablespoons olive oil, add onions and sauté over medium heat until soften.
Add the garlic, diced tomatoes and wine. Continue to cook for 5 minutes.
In an oven safe dish, add 5 tbsp olive oil, place fish fillet on top of olive oil. Sprinkle fish with pepper.
Place tomato slices on filets and top with oregano. Pour the onion/tomato mixture on top of the fish and bake in a preheated 350 degree oven for 40 minutes or until fish flakes easily with a fork.
Remove from oven and top with fresh chopped parsley and a squeeze of lemon juice.