Preheat the oven to 180°C. Grease a baking dish with a little of the olive oil. Clean the two fennel bulbs, remove the tough core, and slice them as thinly as possible. Arrange the sliced fennel in an even layer over the bottom of the dish.
Place the white fish fillet on the layer of fennel. Season the fish with turmeric, pepper, and a pinch of Celtic sea salt. Top the seasoned fish with the four lemon slices and lay the sprigs of fresh dill over it. Finally, drizzle the entire dish with the remaining olive oil.
Cover the baking dish tightly with foil and place it in the middle of the preheated oven. Bake the fish for fifteen to eighteen minutes until cooked through. Remove the foil five minutes before the end of cooking time so excess moisture can evaporate and the dish develops better structure.
Remove the dish from the oven once the white fish is completely cooked and flakes easily. Divide the tender fennel and warm fish directly onto plates and serve immediately.