Apex domains cannot have CNAME records.
Question and response
Question
dig cn. NS
Answer
cn. 5 NS ns.cernet.net.
cn. 5 NS b.dns.cn.
cn. 5 NS a.dns.cn.
cn. 5 NS c.dns.cn.
cn. 5 NS d.dns.cn.
cn. 5 NS e.dns.cn.
Authority
The response has no authority records.
Additional
a.dns.cn. 167812 A 203.119.25.1
b.dns.cn. 168267 A 203.119.26.1
c.dns.cn. 167812 A 203.119.27.1
d.dns.cn. 169929 A 203.119.28.1
e.dns.cn. 72313 A 203.119.29.1
a.dns.cn. 167812 AAAA 2001:dc7:0:0:0:0:0:1
b.dns.cn. 168267 AAAA 2001:dc7:1:0:0:0:0:1
c.dns.cn. 167812 AAAA 2001:dc7:2:0:0:0:0:1
d.dns.cn. 169929 AAAA 2001:dc7:1000:0:0:0:0:1
e.dns.cn. 72313 AAAA 2001:dc7:3:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0