Apex domains cannot have CNAME records.
Question and response
Question
dig cn-globaldns.com. NS
Answer
cn-globaldns.com. 5 NS ns.eu-globaldns.com.
cn-globaldns.com. 5 NS ns100.bh-hosting.com.
cn-globaldns.com. 5 NS ns.au-globaldns.com.
Authority
The response has no authority records.
Additional
ns.au-globaldns.com. 5 A 27.100.36.185
ns.eu-globaldns.com. 5 A 185.99.0.245
ns.au-globaldns.com. 5 AAAA 2402:9e80:1:0:0:0:1:c42c
ns.eu-globaldns.com. 5 AAAA 2a00:8620:2:0:0:0:0:245
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0