Apex domains cannot have CNAME records.
Question and response
Question
dig subsys.no. NS
Answer
subsys.no. 5 NS ns3.subsys.no.
subsys.no. 5 NS ns2.subsys.no.
subsys.no. 5 NS ns1.subsys.no.
Authority
The response has no authority records.
Additional
ns1.subsys.no. 5 A 185.175.56.75
ns2.subsys.no. 5 A 65.108.18.23
ns3.subsys.no. 5 A 31.220.15.158
ns1.subsys.no. 5 AAAA 2a0d:5600:30:1f23:0:0:0:1
ns2.subsys.no. 5 AAAA 2a01:4f9:3071:1c95:0:0:0:2
ns3.subsys.no. 5 AAAA 2a0e:dc0:2:6753:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0