"Legacy" web frameworks like Django, Ruby on Rails or Laravel.
While they won't give you an "advanced" front-end out of the box, the majority of functionality you'd need for an SaaS can be perfectly served by standard HTML and forms, for which those frameworks have excellent support (built-in form validation support, sessions, etc).
I am not aware of any complete full-stack framework that combines the functionality of these backend frameworks with a front-end component. Meteor could be an option but I haven't heard of any big project using it and there's probably a valid reason why.
While they won't give you an "advanced" front-end out of the box, the majority of functionality you'd need for an SaaS can be perfectly served by standard HTML and forms, for which those frameworks have excellent support (built-in form validation support, sessions, etc).
I am not aware of any complete full-stack framework that combines the functionality of these backend frameworks with a front-end component. Meteor could be an option but I haven't heard of any big project using it and there's probably a valid reason why.