- Preheat oven to 220°C. Toss together the tomatoes, garlic, oregano, 1 tablespoon oil, and 1/2 teaspoon salt. Season with pepper. Rub fish with remaining 1 teaspoon oil, dividing evenly. Season inside and outside of fish with remaining 1/2 teaspoon salt; stuff with lemon slices. Arrange in a 22-by-33-cm baking dish with the cherry tomatoes. Roast until fish is cooked through, about 20 minutes; serve immediately.