Apex domains cannot have CNAME records.
Question and response
Question
dig bdo.com.PK. NS
Answer
bdo.com.pk. 5 NS ns1.cyber.net.pk.
bdo.com.pk. 5 NS ns5.cyber.net.pk.
bdo.com.pk. 5 NS csns8.cyber.net.pk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0