Apex domains cannot have CNAME records.
Question and response
Question
dig 0-63.219.29.81.in-addr.arpa. NS
Answer
0-63.219.29.81.in-addr.arpa. 5 NS ns4.msoft-italia.com.
0-63.219.29.81.in-addr.arpa. 5 NS ns2.msoft-italia.com.
0-63.219.29.81.in-addr.arpa. 5 NS ns.msoft-italia.com.
Authority
The response has no authority records.
Additional
ns.msoft-italia.com. 5 A 81.29.219.1
ns2.msoft-italia.com. 5 A 81.29.219.2
ns4.msoft-italia.com. 5 A 69.28.94.85
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0