Cook the noodles in a large saucepan with salted boiling water until they are al dente. Drain and keep warm.
Meanwhile, melt the butter in a saucepan. Sauté the onion pieces and mushroom cubes over a medium heat for 3 minutes. Add the cream and dill. Bring to a boil, turn down the power and simmer for 8-10 minutes. Season to taste with a little salt and freshly ground pepper.
Add the tuna and parmesan and heat. Then add the preheated pasta and mix everything together well. Garnish with a little dill.