Heat the olive oil in a frying pan, and fry half the salami until quite crisp. Add the onion and garlic and cook slowly until the onion is soft. Add the balsamic vinegar, chopped tomatoes, crème fraîche and basil. Mix together, season to taste, and simmer for a few minutes.
Cook the rigatoni according to the packet instructions until al dente. Drain, and drizzle over a little olive oil and seasoning. Tip into a baking dish and pour over the sauce.
Lay the mozzarella over the top with the rest of the salami. Bake in the preheated oven for 25 minutes until golden. Delicious.