Cook the pasta in salted water until al dente. Cook the lentils in water with salt and coriander for 5 to 10 minutes. Dice the onion, sauté in oil until translucent. Add the cream and creme fraiche, reduce until creamy. Add lentils. Season with salt, coriander, cumin and paprika to taste. The sauce should get a nice, pale red color. Fold in the cooked pasta, sprinkle with parmesan if necessary.