Apex domains cannot have CNAME records.
Question and response
Question
dig hubble.nexlinx.net.PK. NS
Answer
hubble.nexlinx.net.pk. 5 NS columbia.nexlinx.net.
hubble.nexlinx.net.pk. 5 NS pathfinder.nexlinx.net.pk.
hubble.nexlinx.net.pk. 5 NS xenon.nexlinx.net.
Authority
The response has no authority records.
Additional
columbia.nexlinx.net. 4 A 216.227.189.113
pathfinder.nexlinx.net.PK. 4 A 202.59.80.10
pathfinder.nexlinx.net.PK. 4 AAAA 2400:68a0:fa15:a100:fa15:a100:666:10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0