How to document your lunch time

How would you go about documenting what time you went to lunch and come back from lunch? Sometimes there are times when someone lies to a superior about how long you took for lunch to try to get you in trouble. Any suggestions on how to cover yourself for something like that? Thanks.
I've never experienced this. I take it you don't clock out for lunches?

Write a note in the emr, "report given to such and such RN" when you leave the floor and "report received, this RN resumed care" or something along those lines when you return.

It's never been an issue in places I've worked. We have always had to clock out for lunches. In the two places where we didn't clock out our lunches were paid, but either way people taking over long lunch breaks has never been a problem. Do you not check out with other staff to let the know you are leaving the floor, back on the floor? I guess write down your lunch times somewhere.