Peel and finely chop the onion. Peel garlic and chop finely. Clean and wash the spinach and put it in boiling salted water. Leave to stand for about 1 minute. Pour onto a sieve and drain well. Put spaghettini in boiling salted water, bring to the boil and cook over medium heat for about 9 minutes. In the meantime cut salmon into strips.
Heat oil in a pan and fry onions and garlic. Deglaze with stock and cream, bring to the boil and stir in cheese, bring to the boil again. Stir in sauce thickener, bring to the boil, fold in salmon and spinach. Season sauce with salt, pepper, sugar and lime juice. Arrange the spaghettini on a plate, spread the sauce over them. Garnish with slices of lime and sprinkle with lemon pepper to taste