Cook the pasta in a large volume of boiling salted water according to the directions on the package. Drain and return the pasta to the saucepan.
In a bowl, mix yogurt, flour, garlic powder, smoked paprika, cayenne and nutmeg.
Add the yogurt mixture, cheese and spinach to the pasta. Mix on low heat until cheese melts. Season with salt and pepper. Add some of the pasta cooking water if sauce is too thick. Serve immediately.