Apex domains cannot have CNAME records.
Question and response
Question
dig optimaitalia.com. NS
Answer
optimaitalia.com. 5 NS ns2.optimaitalia.com.
optimaitalia.com. 5 NS ns1.optimaitalia.com.
Authority
The response has no authority records.
Additional
ns1.optimaitalia.com. 5 A 92.43.240.69
ns2.optimaitalia.com. 5 A 31.15.72.249
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0