Apex domains cannot have CNAME records.
Question and response
Question
dig skillport.com. NS
Answer
skillport.com. 5 NS aur-gtm02.skillport.com.
skillport.com. 5 NS bos-gtm01.skillport.com.
skillport.com. 5 NS bos-gtm02.skillport.com.
skillport.com. 5 NS aur-gtm01.skillport.com.
Authority
The response has no authority records.
Additional
aur-gtm01.skillport.com. 5 A 216.205.88.130
aur-gtm02.skillport.com. 5 A 216.205.88.131
bos-gtm01.skillport.com. 5 A 170.52.44.130
bos-gtm02.skillport.com. 5 A 170.52.44.131
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0