Apex domains cannot have CNAME records.
Question and response
Question
dig rimail.app. NS
Answer
rimail.app. 5 NS dns2.registrar-servers.com.
rimail.app. 5 NS dns1.registrar-servers.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0