Apex domains cannot have CNAME records.
Question and response
Question
dig user-training.com. NS
Answer
user-training.com. 5 NS ns-1119.awsdns-11.org.
user-training.com. 5 NS ns-713.awsdns-25.net.
user-training.com. 5 NS ns-359.awsdns-44.com.
user-training.com. 5 NS ns-1636.awsdns-12.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0