Apex domains cannot have CNAME records.
Question and response
Question
dig ptransmail.com. NS
Answer
ptransmail.com. 5 NS ns-1287.awsdns-32.org.
ptransmail.com. 5 NS ns-589.awsdns-09.net.
ptransmail.com. 5 NS ns-410.awsdns-51.com.
ptransmail.com. 5 NS ns-1752.awsdns-27.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0