Apex domains cannot have CNAME records.
Question and response
Question
dig scannet2.dk. NS
Answer
scannet2.dk. 5 NS ns3.scannet2.dk.
scannet2.dk. 5 NS ns2.scannet2.dk.
scannet2.dk. 5 NS ns.scannet2.dk.
Authority
The response has no authority records.
Additional
ns.scannet2.dk. 5 A 185.25.141.9
ns2.scannet2.dk. 5 A 91.197.248.72
ns.scannet2.dk. 5 AAAA 2a02:2339:4006:10d:0:0:4171:4171
ns2.scannet2.dk. 5 AAAA 2a02:2339:1:112:0:5:1:b11
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0