Apex domains cannot have CNAME records.
Question and response
Question
dig tele.dk. NS
Answer
tele.dk. 5 NS auth01.ns.tele.dk.
tele.dk. 5 NS ns-soa.darenet.dk.
tele.dk. 5 NS auth02.ns.tele.dk.
Authority
The response has no authority records.
Additional
auth01.ns.tele.dk. 5 A 62.243.0.166
auth02.ns.tele.dk. 5 A 194.192.207.166
ns-soa.darenet.dk. 5 A 130.226.179.50
auth01.ns.tele.dk. 5 AAAA 2001:6c8:2:400:0:0:0:166
auth02.ns.tele.dk. 5 AAAA 2001:6c8:4:400:0:0:0:166
ns-soa.darenet.dk. 5 AAAA 2001:878:0:e000:82:e2:b3:32
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0