Clean the spinach, wash thoroughly several times and let it drip off a little. Peel onion and garlic. Chop the onion finely, press the garlic through a garlic press. Prepare rice in boiling salted water according to package instructions.
Heat 15 g fat in a pot, fry garlic and 2/3 of the onions in it. Add the spinach, cover and let it collapse in 4-5 minutes. Season with salt, pepper and nutmeg and steam covered for about 5 minutes.
Heat 25 g fat in a small pot, sauté the remaining onions in it, dust with flour and sauté briefly. Add stock and milk while stirring and bring to the boil. Let the sauce simmer for about 5 minutes.
Wash lemon thoroughly, grate dry, finely grate peel. Halve the lemon and squeeze one half. Stir the lemon peel into the sauce and season to taste with salt, pepper and approx. 2 tablespoons of lemon juice.
Wash the salmon fillet, dab dry and cut into 8-12 thin slices. Heat 20 g fat in a large, coated pan. Fry salmon slices for 2-3 minutes on each side. Season with salt and pepper.
Arrange salmon, spinach and rice with the lemon sauce on plates. Serve garnished with lemon.