Apex domains cannot have CNAME records.
Question and response
Question
dig am-uddannelsen.dk. NS
Answer
am-uddannelsen.dk. 4 NS ns01.one.com.
am-uddannelsen.dk. 4 NS ns02.one.com.
Authority
The response has no authority records.
Additional
ns01.one.com. 3 A 195.206.121.10
ns02.one.com. 3 A 185.10.11.10
ns01.one.com. 3 AAAA 2001:67c:28cc:0:0:0:0:10
ns02.one.com. 3 AAAA 2001:67c:3c0:0:0:0:0:10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0