Apex domains cannot have CNAME records.
Question and response
Question
dig sparkmail.it. NS
Answer
sparkmail.it. 5 NS edward.ns.cloudflare.com.
sparkmail.it. 5 NS imani.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0