Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8-10 minutes or until al dente. Drain.
In a large skillet, brown beef and onion. Drain. Add spaghetti sauce and simmer for 15 minutes.
Preheat oven to 350º. In a lightly greased 2 quart baking dish, place about half of the pasta. Top with a layer of provolone and mozzarella cheese slices. Spread on a layer of spaghetti sauce mixture and sour cream. Cover with remaining pasta, cheese and sauce. Sprinkle a layer of parmesan cheese and fresh basil.