Apex domains cannot have CNAME records.
Question and response
Question
dig 4bone.mynet.it. NS
Answer
4bone.mynet.it. 5 NS rdns1.mynet.it.
4bone.mynet.it. 5 NS rdns2.mynet.it.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0