I'm using pointDNS
I have an alias: xxx.com to the xxx.herokudns.com.
Now I have added a CNAME www.xxx.com and redirected it to xxx.herokudns.com (also tried xxx.com with the same result).
What I want is that the www disappears in the URL bar in the browser and I only see xxx.com
nslookup xxx.com
OK
nslookup www.xxx.com
Non-authoritative answer:
www.xxx.com canonical name = xxx.com.
..
The above seems really fine to me, but why is the www still in my browser? Or do I have to handle this somewhere else? I configured it as described here: https://support.dnsimple.com/articles/redirect-heroku/
this is not related to your DNS settings directly, you have to implement redirect in your app.
another way, if it is not possible to fix the app - you can use cloudflare and setup forwarding rule there, using page rules.