Apex domains cannot have CNAME records.
Question and response
Question
dig mystpaul.com. NS
Answer
mystpaul.com. 5 NS ns-819.awsdns-38.net.
mystpaul.com. 5 NS ns-1989.awsdns-56.co.uk.
mystpaul.com. 5 NS ns-626.awsdns-14.net.
mystpaul.com. 5 NS ns-1245.awsdns-27.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0