The following outlines how to setup Heroku + Cloudflare with a full SSL certificate. What this means is that communication between the browser and the Cloudflare CDN is encrypted as well as communication between Cloudflare and Heroku’s origin server. Follow these steps exactly and the setup is a breeze.
First you want to add the root domain and the www domain to heroku. You do this by clicking into your production application, then going to settings and then scrolling down to Domains and certificates.
Here you will add <your_domain>.com and www.<your_domain>.com. This will give you two CNAME records. They will look something like <your_domain>.com.herokudns.com and www.<your_domain>.com.herokudns.com.