Apex domains cannot have CNAME records.
Question and response
Question
dig ip263.fastwebnet.it. NS
Answer
ip263.fastwebnet.it. 5 NS dns4.fastweb.it.
ip263.fastwebnet.it. 5 NS dns3.fastweb.it.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0