Apex domains cannot have CNAME records.
Question and response
Question
dig airmail.no. NS
Answer
airmail.no. 1 NS ns2.netclient.no.
airmail.no. 1 NS ns1.netclient.no.
Authority
The response has no authority records.
Additional
ns1.netclient.no. 1 A 213.179.41.143
ns2.netclient.no. 1 A 213.162.232.67
ns1.netclient.no. 1 AAAA 2001:820:2:0:0:0:0:5
ns2.netclient.no. 1 AAAA 2a01:160:dfff:dfff:0:525a:e29:4b62
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0