Bring the water with salt to the boil and cook the spaghetti until al dente according to the instructions on the packet.
In the meantime, wash the salmon fillets, dry them and fry them in olive oil in a non-stick pan over low heat. Season with salt and pepper.
Peel the avocado, remove the stone and puree in a blender with lemon juice and salt and pepper. The consistency is still firm, so remove and add so much of the pasta water that the result is a bulky mass. Depending on your preference, you can stir it like a pesto, firm or creamy.
When done, drain the pasta and stir in the avocado mixture. Arrange on a plate. Tear up the fried salmon and distribute it on the plates.