Apex domains cannot have CNAME records.
Question and response
Question
dig alidns.com. NS
Answer
alidns.com. 5 NS ns5.aliyun.com.
alidns.com. 5 NS ns4.aliyun.com.
alidns.com. 5 NS ns3.aliyun.com.
Authority
The response has no authority records.
Additional
ns3.aliyun.com. 5 A 106.11.35.29
ns3.aliyun.com. 5 A 106.11.35.30
ns3.aliyun.com. 5 A 106.11.41.153
ns3.aliyun.com. 5 A 106.11.41.154
ns4.aliyun.com. 5 A 140.205.122.133
ns4.aliyun.com. 5 A 140.205.122.143
ns5.aliyun.com. 5 A 47.88.74.34
ns5.aliyun.com. 5 A 47.241.207.14
ns5.aliyun.com. 5 A 140.205.122.153
ns3.aliyun.com. 5 AAAA 2401:b180:4100:0:0:0:0:11
ns4.aliyun.com. 5 AAAA 2401:b180:4100:0:0:0:0:12
ns5.aliyun.com. 5 AAAA 2401:b180:4100:0:0:0:0:13
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0