Apex domains cannot have CNAME records.
Question and response
Question
dig cie.ac. NS
Answer
cie.ac. 5 NS ns2.cie.ac.
cie.ac. 5 NS ns1.cie.ac.
cie.ac. 5 NS ns3.cie.ac.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0