Apex domains cannot have CNAME records.
Question and response
Question
dig delta-telecom.net. NS
Answer
delta-telecom.net. 5 NS ns01.azersat.com.
delta-telecom.net. 5 NS ns02.azersat.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0