Apex domains cannot have CNAME records.
Question and response
Question
dig th.seeweb.it. NS
Answer
th.seeweb.it. 5 NS ns2.th.seeweb.it.
th.seeweb.it. 5 NS ns1.th.seeweb.it.
Authority
The response has no authority records.
Additional
ns1.th.seeweb.it. 5 A 217.64.201.170
ns2.th.seeweb.it. 5 A 95.174.18.147
ns2.th.seeweb.it. 5 AAAA 2001:4b78:2100:2:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0