Apex domains cannot have CNAME records.
Question and response
Question
dig renvixo.com. NS
Answer
renvixo.com. 5 NS ns1.renvixo.com.
renvixo.com. 5 NS ns2.renvixo.com.
Authority
The response has no authority records.
Additional
ns1.renvixo.com. 5 A 216.245.202.162
ns2.renvixo.com. 5 A 216.245.202.163
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0