Steps
1. Heat olive oil in a saucepan over medium heat.
2. Add chopped onion and minced garlic, sauté until softened.
3. Stir in the diced tomato and cook for 2-3 minutes until it breaks down slightly.
4. Pour in the fish stock and bring to a gentle simmer.
5. Add the white fish fillet and basil, cooking for about 5-7 minutes until the fish is cooked through.
6. Season with salt and pepper to taste.
7. Serve hot, garnished with fresh parsley if desired.