Apex domains cannot have CNAME records.
Question and response
Question
dig ip99.fastwebnet.it. NS
Answer
ip99.fastwebnet.it. 5 NS dns3.fastweb.it.
ip99.fastwebnet.it. 5 NS dns4.fastweb.it.
Authority
The response has no authority records.
Additional
dns3.fastweb.it. 5 A 85.18.87.69
dns4.fastweb.it. 5 A 213.140.22.93
dns3.fastweb.it. 5 AAAA 2001:b00:4:5:3:0:0:0
dns4.fastweb.it. 5 AAAA 2001:b00:4:8:3:0:0:0
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0