In a large skillet, brown chicken in butter on each side. Remove and set aside. Add onion and garlic; saute until tender. Stir in tomatoes and salt. Bring to a boil. Reduce heat; return chicken to pan. Cover and simmer for 30 minutes or until chicken juices run clear.
Remove chicken and keep warm. Combine the flour and sour cream. Reduce heat to low; stir in sour cream mixture and Parmesan cheese. Heat through (do not boil). Serve chicken and sauce over noodles.