Preheat the oven to 450°F.

Grease a baking dish using a tablespoon of olive oil.

Place the potatoes in the dish and mix well with salt, black pepper, and a tablespoon of olive oil. Roast the potatoes for 20 to 25 minutes until tender.

Pour a tablespoon of olive oil and the butter into a medium pot, heat up and add the chopped onion once the butter has melted. Cook, stirring occasionally, for about 5 minutes over medium heat.

Add the garlic and cook for one more minute until it starts to smell.

Incorporate the seasonings, rosemary sprigs, capers, lemon zest, cayenne pepper, and Dijon mustard, the broth, and the cream. Bring to medium-high heat and when it begins to boil, reduce the heat to medium-low. Let it cook this way for 5 minutes until it starts to thicken.

Sprinkle salt over the cod pieces.

Remove the potatoes from the oven, place the fish on top, and pour the sauce over it, cook uncovered for another 10 to 15 minutes.

Remove from the oven, add finely chopped parsley on top and serve hot.

Enjoy!