Wash the salmon fillet, dab dry and sprinkle with 2 tablespoons of lemon juice. Sprinkle with salt and leave to stand for a while. Sort the spinach and wash thoroughly. Peel onion and garlic.
Finely dice onion, press garlic through a garlic press. Heat 20 g fat in a pot, fry onion and garlic in it until transparent. Add spinach, sauté and let it collapse. Season with salt, pepper and nutmeg.
Heat 40 g fat in a pot, sauté flour in it and deglaze with broth and milk. Add lemon peel and simmer for a few minutes while stirring. Season with salt, pepper and remaining lemon juice.
Mix the egg yolks with a little hot sauce, then stir into the rest of the sauce. Remove from heat. Pour some sauce into a greased casserole dish, place lasagne sheets, salmon fillet, lasagne sheets, sauce, spinach, lasagne sheets, and finally layer the rest of the sauce.
Sprinkle with parmesan and spread the remaining fat in flakes on the lasagne. Bake in the preheated oven (electric: 200 °C / gas: level 3) for 40-45 minutes. Serve garnished with lemon wheels and lemon balm.