Apex domains cannot have CNAME records.
Question and response
Question
dig mydsl.it. NS
Answer
mydsl.it. 4 NS ns2.mydsl.it.
mydsl.it. 4 NS ns1.mydsl.it.
Authority
The response has no authority records.
Additional
ns1.mydsl.it. 4 A 80.68.177.90
ns2.mydsl.it. 4 A 80.68.177.40
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0