Apex domains cannot have CNAME records.
Question and response
Question
dig pcixp.com. NS
Answer
pcixp.com. 5 NS ns-850.awsdns-42.net.
pcixp.com. 5 NS ns-1328.awsdns-38.org.
pcixp.com. 5 NS ns-655.awsdns-17.net.
pcixp.com. 5 NS ns-1150.awsdns-15.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0