Cook the pasta according to the instructions on the package.
Melt the butter in a pan, add the sugar and caramelize briefly. Halve the asparagus spears and cut into 3 cm long pieces. Put the asparagus pieces in the pan and fry lightly for five minutes.
Add the finely chopped onions, finely chopped salmon and quartered tomatoes and sauté for another five minutes. Season with salt, pepper and lemon juice. Deglaze with the wine and simmer over medium heat for about 10 minutes. Gradually add the washed spinach until it has collapsed.
Finally stir in the cream and sour cream and season again with salt, pepper and nutmeg. Mix the pasta in the pan and serve.