Apex domains cannot have CNAME records.
Question and response
Question
dig reg.az. NS
Answer
reg.az. 5 NS ns1.online.az.
reg.az. 5 NS ns3.online.az.
Authority
The response has no authority records.
Additional
ns1.online.az. 5 A 217.14.97.30
ns3.online.az. 5 A 148.251.2.235
ns1.online.az. 5 AAAA 2a00:7da0:0:0:200:0:0:6
ns3.online.az. 5 AAAA 2a01:4f8:201:52f3:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0