Preheat your Oven to 400°F. Lightly grease a Baking Dish large enough to hold all 4 fillets in a single layer without overlapping.

Pat the 4 cod fillets (每片约6盎司，擦干) completely dry with paper towels — this is key for a good texture and helps the 3 tbsp unsalted butter, 融化 sauce cling to the fish. Season both sides lightly with ¾ tsp salt and ¾ tsp salt, then arrange them in the prepared Baking Dish.

In a small Mixing Bowl, whisk together the melted 3 tbsp unsalted butter, 融化, 2 tbsp olive oil, minced 3 cloves of garlic, 切碎, 1 lemon juice, 削皮 (约3汤匙果汁), 1 tsp lemon zest, 削皮 (来自上述柠檬), 2 tbsp parsley, 细切，新鲜, 1 tbsp dill, 细切，新鲜 (if using), dried 1 tsp oregano, ¼ tsp paprika, 烟熏, ¾ tsp salt, and ¾ tsp salt until combined.

Spoon and spread the lemon-herb 3 tbsp unsalted butter, 融化 evenly over the top of each fillet, making sure every piece is well coated. If using 1 lemon juice, 削皮 (约3汤匙果汁) slices, lay 1–2 thin slices on top of each fillet.

Bake uncovered for 12–15 minutes, depending on the thickness of your fillets. The fish is done when it flakes easily with a fork and is opaque all the way through. A 1-inch thick fillet takes about 15 minutes. Do not overbake — cod turns dry and rubbery quickly.

Remove from the Oven and let rest for 2 minutes. Spoon the pan juices over the fillets, scatter with fresh 2 tbsp parsley, 细切，新鲜, and serve immediately with your choice of sides.