Apex domains cannot have CNAME records.
Question and response
Question
dig ritmail.at. NS
Answer
ritmail.at. 5 NS ns0115.secondary.cloudflare.com.
ritmail.at. 5 NS ns0233.secondary.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0