Apex domains cannot have CNAME records.
Question and response
Question
dig portal.gigtel.com. NS
Answer
portal.gigtel.com. 5 NS pns102.cloudns.net.
portal.gigtel.com. 5 NS pns104.cloudns.net.
portal.gigtel.com. 5 NS pns101.cloudns.net.
portal.gigtel.com. 5 NS pns103.cloudns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0