Cook the fusilli in salted water until al dente. Melt the butter in a saucepan and sauté the onion in it over a low heat for about 5 minutes until soft. Stir occasionally. Deglaze with wine and reduce by two thirds. Stir in the cream and season with salt and pepper. Simmer until the sauce thickens slightly. Cut the smoked salmon into pieces and stir in with the dill tips and lemon juice to taste.
Drain the pasta and place in a warmed serving bowl. Pour over the salmon sauce and mix well. Garnish with dill tips.