Apex domains cannot have CNAME records.
Question and response
Question
dig cernet.cn. NS
Answer
cernet.cn. 4 NS dns1.cernet.cn.
cernet.cn. 4 NS dns2.cernet.cn.
Authority
The response has no authority records.
Additional
dns1.cernet.cn. 4 A 202.205.109.1
dns2.cernet.cn. 4 A 202.205.11.9
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0