How to properly set up a ru-center for a domain without www?

Question

Domain Name System

I'm trying to get the domain from the ru-center to work with the application on heroku without www. Everything is fine with the prefix, I registered the canonical name in CNAME (www cname app.heroku.com.) but I can’t figure it out with www.
Here on the Toaster flashed advice to prescribe a canonical like www.myapp.com. cname app.heroku.com., but the registrar does not allow me to do this - it shows an error. You can't set up a forward from your personal account. Advise, please, something.

Answer 1

@ CNAME app.heroku.com.