Apex domains cannot have CNAME records.
Question and response
Question
dig pi.cnr.it. NS
Answer
pi.cnr.it. 2 NS dns2.ba.cnr.it.
pi.cnr.it. 2 NS nameserver.cnr.it.
pi.cnr.it. 2 NS ns1.surfnet.nl.
pi.cnr.it. 2 NS ns2.iit.cnr.it.
pi.cnr.it. 2 NS ns1.iit.cnr.it.
Authority
The response has no authority records.
Additional
nameserver.cnr.it. 2 A 194.119.192.34
nameserver.cnr.it. 2 AAAA 2a00:1620:c0:220:194:119:192:34
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0