I couldn’t find any support documentation on this, but that might because it’s a very simple question and I just don’t have a grasp on how CloudFlare really works yet.
Say someone visits a website using CloudFlare’s services and enters a password. Does CloudFlare see that password in plaintext? If not why not? Is TLS between the end user and the website, or between the end user and CloudFlare? Does this depend on the settings, what difference do theses make on what CloudFlare sees?