Peel the onions and cut them into rings. Place in a flat baking dish, place the salmon on top, pepper.
Pour wine over until the fish is completely covered. Cook in the preheated oven on the middle rack at 200 degrees for about 25 minutes.
In the meantime, heat the cream in a saucepan. Season with 4 teaspoons of mustard and 4 teaspoons of honey (more if you like) and simmer until the sauce is thick.