Apex domains cannot have CNAME records.
Question and response
Question
dig cet.com. NS
Answer
cet.com. 4 NS ns1.cet.com.
cet.com. 4 NS ns0.cet.com.
Authority
The response has no authority records.
Additional
ns0.cet.com. 4 A 69.41.128.7
ns1.cet.com. 4 A 69.41.129.7
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0