Apex domains cannot have CNAME records.
Question and response
Question
dig azure-dns.cn. NS
Answer
azure-dns.cn. 4 NS ns3-01.azure-dns.cn.
azure-dns.cn. 4 NS ns4-02.azure-dns.cn.
azure-dns.cn. 4 NS ns1-01.azure-dns.cn.
azure-dns.cn. 4 NS ns2-02.azure-dns.cn.
Authority
The response has no authority records.
Additional
ns1-01.azure-dns.cn. 4 A 40.73.192.1
ns2-02.azure-dns.cn. 4 A 40.73.194.2
ns3-01.azure-dns.cn. 4 A 40.73.196.1
ns4-02.azure-dns.cn. 4 A 40.73.198.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0