If you need the debug output of the puppetmaster running with passenger you have to uncomment this setting in the config.ru:
#ARGV << "--debug"
If you don't know where your config.ru is, check the Apache DocumentRoot. It's in /path/to/DocumentRoot/../config.ru. For example if your DocumentRoot is /etc/puppet/rack/public/ the config.ru is in /etc/puppet/rack/config.ru.
