Apex domains cannot have CNAME records.
Question and response
Question
dig sjon.at. NS
Answer
sjon.at. 5 NS ns2.cnh.at.
sjon.at. 5 NS ns1.cnh.at.
sjon.at. 5 NS ns3.cnh.at.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0