Apex domains cannot have CNAME records.
Question and response
Question
dig cibex.net. NS
Answer
cibex.net. 5 NS dns1.telekom.at.
cibex.net. 5 NS dns3.telekom.at.
cibex.net. 5 NS dns2.telekom.at.
Authority
The response has no authority records.
Additional
dns1.telekom.at. 5 A 80.120.17.26
dns2.telekom.at. 5 A 192.174.68.105
dns2.telekom.at. 5 A 213.33.99.79
dns3.telekom.at. 5 A 176.97.158.105
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0