Apex domains cannot have CNAME records.
Question and response
Question
dig semacustomers.it. NS
Answer
semacustomers.it. 5 NS ns03.semacustomers.it.
semacustomers.it. 5 NS ns01.semacustomers.it.
Authority
The response has no authority records.
Additional
ns01.semacustomers.it. 5 A 217.172.4.129
ns03.semacustomers.it. 5 A 193.178.235.27
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0