Apex domains cannot have CNAME records.
Question and response
Question
dig ri.mu. NS
Answer
ri.mu. 4 NS ns2.rimuhosting.com.
ri.mu. 4 NS ns1.rimuhosting.com.
Authority
The response has no authority records.
Additional
ns1.rimuhosting.com. 4 A 66.199.228.130
ns2.rimuhosting.com. 4 A 206.123.113.132
ns2.rimuhosting.com. 4 AAAA 2605:7700:0:200:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0