Apex domains cannot have CNAME records.
Question and response
Question
dig 128.28.185.194.in-addr.arpa. NS
Answer
128.28.185.194.in-addr.arpa. 5 NS ns3a.idcservices.it.
128.28.185.194.in-addr.arpa. 5 NS ns4a.idcservices.it.
Authority
The response has no authority records.
Additional
ns3a.idcservices.it. 5 A 194.20.8.4
ns4a.idcservices.it. 5 A 194.20.8.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0