Melt the butter for the sauce. Add onions and garlic and sauté in them. Add the paprika and sauté. Pour in the stock and simmer covered for 10 minutes, then puree. Stir in the crème fraîche and spices. May happen if necessary.
Cook the pasta in salted water until al dente.
Heat the butter in a pan and fry the diced paprika in it. Add the drained pasta and season. Pour sour cream over it. Serve with the sauce.