Apex domains cannot have CNAME records.
Question and response
Question
dig thera.it. NS
Answer
thera.it. 4 NS ns1mi.infracom.it.
thera.it. 4 NS ns2mi.infracom.it.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0