Yes it's possible - I have several exes who I am very good friends with - break initiated by either party - and no unresolved romantic feelings on either side.
However, it depends a lot on the underlying friendship in the relationship and why you broke up and whether you have unresolved issues about the break up - the perennial 'but why' question. While that persists and you don't manage to either find the 'true' reason or an explanation which satisfies you - then it is not a 'pure' friendship as there are still unresolved issues.
I will say though that it can take quite a bit of time - several months or so in my experience - to adjust to this situation - especially if you're the one that didn't do the breaking! Like don't expect to be 'best friends forever' on a Monday - or even a month on Monday - if you were dumped on a Saturday!!