Peel and finely dice the onion and garlic. Heat 1 tablespoon of oil. Sauté onion and garlic in it. Add frozen spinach and 100 ml water, cover and allow to defrost over medium heat for 14-16 minutes.
For the pasta, boil 3 l of salted water. Rinse salmon, dab dry and cut into 4 pieces. Season with salt. Heat 1 tablespoon of oil in a frying pan. Fry the salmon for 2-3 minutes on each side.
Season with coarse pepper and keep warm in the pan.
Meanwhile cook the pasta in boiling salted water for 2-3 minutes. Drain. Season spinach with salt and pepper. Stir in 2 tablespoons of oil and lemon juice. Fold in the noodles. Serve everything.