Apex domains cannot have CNAME records.
Question and response
Question
dig chinacloudapi.cn. NS
Answer
chinacloudapi.cn. 2 NS ns4-201.azure-dns-3.cn.
chinacloudapi.cn. 2 NS ns1-201.azure-dns-3.cn.
chinacloudapi.cn. 2 NS ns2-201.azure-dns-3.cn.
chinacloudapi.cn. 2 NS ns3-201.azure-dns-3.cn.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0