Apex domains cannot have CNAME records.
Question and response
Question
dig cer.net. NS
Answer
cer.net. 4 NS dns.edu.cn.
cer.net. 4 NS ns2.net.edu.cn.
Authority
The response has no authority records.
Additional
dns.edu.cn. 4 A 202.38.109.35
dns.edu.cn. 4 AAAA 2001:250:c006:0:0:0:0:35
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0