Apex domains cannot have CNAME records.
Question and response
Question
dig protection.partner.outlook.cn. NS
Answer
protection.partner.outlook.cn. 4 NS ns1-36.azure-dns.cn.
protection.partner.outlook.cn. 4 NS ns3-36.azure-dns.cn.
protection.partner.outlook.cn. 4 NS ns2-36.azure-dns.cn.
protection.partner.outlook.cn. 4 NS ns4-36.azure-dns.cn.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0