You want to manage one or more entries in a file located under "/etc/cron.*"
Manage the entire crontab file. As a single file, a concat, a define or via Augeas.
The built in Puppet type only manages per user crontab files (the kind
that exist under /var/spool/cron on Linux). There is currently no built
in way to explicitly manage cron file entries under /etc, although you
can use many of the other types as a work around.
The easiest way to do this is with a file resource, with either static
text or via a template, that simply contains the whole contents of
the cron entry. This doesn't provide any specific validation or
abstraction but it is very easy to do.