Apex domains cannot have CNAME records.
Question and response
Question
dig um-pm.com. NS
Answer
um-pm.com. 4 NS ns-1302.awsdns-34.org.
um-pm.com. 4 NS ns-988.awsdns-59.net.
um-pm.com. 4 NS ns-243.awsdns-30.com.
um-pm.com. 4 NS ns-1858.awsdns-40.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0