How to configure Phusion Passenger X-frame options?

I'm trying to iframe a site I built (using Rails) and deployed on an ubuntu instance on AWS using Phusion Passenger.

I looked more into it and found that I need to change my X-frame options, a HTTP header from 'SAME ORIGIN' to 'ALLOWALL'. I already added this line into my config/application.rb file and my config/environments/production.rb

config.action_dispatch.default_headers.merge!({'X-Frame-Options' => 'ALLOWALL'})

Even then, when I open my site, I still get these settings in my Network Headers:

Status:200 OK
Transfer-Encoding:chunked
X-Content-Type-Options:nosniff
X-Frame-Options:SAMEORIGIN
X-Powered-By:Phusion Passenger 5.0.11

This leads me to believe that there's a Phusion Passenger config file somewhere that I need to change the X-Frame-Options for. Any clues or help would be great, thanks!