Apex domains cannot have CNAME records.
Question and response
Question
dig i2.dk. NS
Answer
i2.dk. 5 NS orion.i2.dk.
i2.dk. 5 NS mimer.deic.dk.
i2.dk. 5 NS ns-soa.darenet.dk.
Authority
The response has no authority records.
Additional
mimer.deic.dk. 5 A 95.128.27.66
orion.i2.dk. 5 A 78.153.182.90
ns-soa.darenet.dk. 5 A 130.226.179.50
mimer.deic.dk. 5 AAAA 2001:87f:ff27:65:0:0:0:66
ns-soa.darenet.dk. 5 AAAA 2001:878:0:e000:82:e2:b3:32
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0