Steam the onions and spinach in 1 tablespoon of olive oil and season with salt and pepper.
Season the cod with lemon juice, salt and pepper and place in a greased dish. Now the spinach mixture is spread over the fish. Mix the cheese and crème fraîche together and spread over the spinach. To finish, sprinkle with flaked almonds.
Gratinate in the oven (center, fan oven) at 225 degrees for 10 minutes.