the site seems to be throwing an application error from heroku. now correct me if i'm wrong, but isn't cloudflare supposed to be a caching proxy? and if i am correct, why am i even getting to the actual server? is it this dude doesn't have cloudflare configured correctly? if anyone can explain this i would love to know so i don't make the same mistake in the future.
Some CDN software actively thwarts Cloudflare with things like Pragma: no-cache or Cache-Control: no-cache, or bad Expires settings for static assets. Spend some time learning cache headers and then do some testing to see what actually produces a "hit" to the web server under the cache, and how long the various caches (browser, cloudflare, app, etc) last.