Apex domains cannot have CNAME records.
Question and response
Question
dig tls-rpt.tech. NS
Answer
tls-rpt.tech. 5 NS ns-1676.awsdns-17.co.uk.
tls-rpt.tech. 5 NS ns-548.awsdns-04.net.
tls-rpt.tech. 5 NS ns-54.awsdns-06.com.
tls-rpt.tech. 5 NS ns-1121.awsdns-12.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0