Apex domains cannot have CNAME records.
Question and response
Question
dig complea-hosting.dk. NS
Answer
complea-hosting.dk. 3 NS ns3.complea-hosting.dk.
complea-hosting.dk. 3 NS ns1.complea-hosting.dk.
complea-hosting.dk. 3 NS ns2.complea-hosting.dk.
Authority
The response has no authority records.
Additional
ns1.complea-hosting.dk. 3 A 185.163.185.180
ns2.complea-hosting.dk. 3 A 185.163.185.190
ns3.complea-hosting.dk. 3 A 77.68.236.172
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0