Cook the tagliatelle in salted water until al dente. Meanwhile, sauté the chopped onion in a little butter until translucent. Add the halved tomatoes. Add brandy, a good shot of white wine and whipped cream and bring to the boil. Season with salt and pepper and whisk the sauce until smooth. Cut the smoked salmon into strips, add to the hot sauce and remove from the heat. Drain the pasta, let it drain and mix it into the smoked salmon sauce. Stir in the chopped dill and arrange in a warmed dish. Sprinkle with freshly grated Parmesan.