Sprinkle fish with salt, pepper and lemon juice. Allow to stand for about 10 minutes while you prepare the other products. Heat a little oil and lightly fry the fish on both sides as to tighten. Remove it and arrange in a baking dish. In the same oil fry the onion, finely chopped. Once softened, add the mushrooms cut into slices. Add salt and pepper and leave to cook and soften. When the mushrooms are ready, add the flour and cook for about 1 minute, stirring constantly. Add the cream and mix again until it begins to simmer - if the sauce has become thick, you can dilute it with a little milk. Chop the dill finely and add to the sauce. Mix well and remove from heat. Pour the finished sauce over the fish steaks. Bake for about 30 minutes in a preheated 180 C oven. Serve with a side of fries or mashed potatoes. * The original recipe fish baked in the oven and served with mushroom sauce fields. At home we prefer top option.