01 - Preheat the oven to 400°F and lightly grease a baking dish large enough to hold the fillets in a single layer.
02 - Pat the cod fillets dry with paper towels, then season both sides evenly with salt and freshly ground black pepper. Arrange them in the prepared baking dish.
03 - In a small bowl, whisk together the melted butter, olive oil, lemon juice, lemon zest, and minced garlic until well combined.
04 - Pour the lemon butter sauce evenly over the cod fillets, then sprinkle with chopped parsley and optional dill.
05 - Place the baking dish in the oven and bake for 15 to 20 minutes, or until the fish flakes easily with a fork and is opaque throughout.
06 - Remove from the oven, spoon pan sauce over the fillets, and garnish with fresh lemon slices and additional herbs. Serve immediately.