Preheat the oven to 400°F (200°C).

Arrange the 3 cod filets cut in half (6 pieces total) in a 13 x 9 x 2-inch baking dish in a single layer. Pat the fish dry if needed and season both sides with salt and pepper to taste.

In a small bowl, whisk together ¼ cup unsalted melted butter, 1 tablespoon olive oil, 3 minced garlic cloves, and 1 tablespoon Cajun seasoning until well combined.

Brush or spoon the butter mixture evenly over the tops and sides of each filet so they are well coated.

Bake in the preheated oven for about 15 minutes, or until the fish is opaque throughout and flakes easily with a fork.

Remove from the oven and let the filets rest for 1–2 minutes before serving.