Apex domains cannot have CNAME records.
Question and response
Question
dig seo.it. NS
Answer
seo.it. 5 NS ns20.tuonomeregistrar.net.
seo.it. 5 NS ns9.tuonomeregistrar.com.
Authority
The response has no authority records.
Additional
ns9.tuonomeregistrar.com. 5 A 151.11.83.9
ns20.tuonomeregistrar.net. 5 A 46.37.17.20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0