Apex domains cannot have CNAME records.
Question and response
Question
dig rm.cnr.it. NS
Answer
rm.cnr.it. 5 NS nameserver.cnr.it.
rm.cnr.it. 5 NS nameserver2.rm.cnr.it.
rm.cnr.it. 5 NS dns.cnr.it.
rm.cnr.it. 5 NS nameserver.rm.cnr.it.
Authority
The response has no authority records.
Additional
dns.cnr.it. 5 A 150.146.205.10
nameserver.cnr.it. 5 A 194.119.192.34
nameserver.cnr.it. 5 AAAA 2a00:1620:c0:220:194:119:192:34
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0