Apex domains cannot have CNAME records.
Question and response
Question
dig cs.nttpc.info. NS
Answer
cs.nttpc.info. 4 NS ns-518.awsdns-00.net.
cs.nttpc.info. 4 NS ns-1950.awsdns-51.co.uk.
cs.nttpc.info. 4 NS ns-16.awsdns-02.com.
cs.nttpc.info. 4 NS ns-1461.awsdns-54.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0