Apex domains cannot have CNAME records.
Question and response
Question
dig deltatelecom.az. NS
Answer
deltatelecom.az. 4 NS ns01.azersat.com.
deltatelecom.az. 4 NS ns02.azersat.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0