Apex domains cannot have CNAME records.
Question and response
Question
dig posprints.com. NS
Answer
posprints.com. 4 NS ns-1293.awsdns-33.org.
posprints.com. 4 NS ns-1800.awsdns-33.co.uk.
posprints.com. 4 NS ns-1116.awsdns-11.org.
posprints.com. 4 NS ns-1518.awsdns-61.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0