For the pasta, boil 3-4 l salted water. Wash the salmon, dab dry and dice. Sprinkle with 1 tbsp lemon juice. Peel and chop the onion. Cook pasta in boiling salted water according to package instructions.
In the meantime heat oil in a pan. Sauté the onion in it. Fry the salmon for 2-3 minutes. Take off about 100 ml of the pasta water with a ladle and pour it into the salmon. Stir in sour cream and the rest of the lemon juice, bring to the boil and simmer for 3-4 minutes.
Add frozen peas after 1 minute.
Wash the dill, chop finely and stir into the sauce. Season with salt, pepper and approx. 1⁄2 tsp. sugar. Drain noodles, mix carefully with the sauce and serve. Serve with lemon wedges.