Apex domains cannot have CNAME records.
Question and response
Question
dig koedrift.dk. NS
Answer
koedrift.dk. 5 NS ns2.koedrift.dk.
koedrift.dk. 5 NS ns3.koedrift.dk.
koedrift.dk. 5 NS ns1.koedrift.dk.
Authority
The response has no authority records.
Additional
ns1.koedrift.dk. 5 A 217.30.38.181
ns2.koedrift.dk. 5 A 217.30.38.27
ns3.koedrift.dk. 5 A 217.30.38.30
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0