1. Preheat oven to 400°F (200°C).
2. Season the fish with salt and pepper.
3. Heat the olive oil in a large skillet over medium heat. Add the fish and cook for 2-3 minutes per side, or until golden brown.
4. Transfer the fish to a greased baking dish.
5. Scatter the red onion, garlic, parsley, tomatoes, and lemon slices over the fish.
6. Bake for 15-20 minutes, or until the fish is cooked through.
7. Serve immediately with your favorite sides.
