Apex domains cannot have CNAME records.
Question and response
Question
dig sign.co.it. NS
Answer
sign.co.it. 2 NS crystal.ns.cloudflare.com.
sign.co.it. 2 NS kurt.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
kurt.ns.cloudflare.com. 2 A 108.162.193.193
kurt.ns.cloudflare.com. 2 A 172.64.33.193
kurt.ns.cloudflare.com. 2 A 173.245.59.193
crystal.ns.cloudflare.com. 2 A 108.162.194.202
crystal.ns.cloudflare.com. 2 A 162.159.38.202
crystal.ns.cloudflare.com. 2 A 172.64.34.202
kurt.ns.cloudflare.com. 2 AAAA 2606:4700:58:0:0:0:adf5:3bc1
kurt.ns.cloudflare.com. 2 AAAA 2803:f800:50:0:0:0:6ca2:c1c1
kurt.ns.cloudflare.com. 2 AAAA 2a06:98c1:50:0:0:0:ac40:21c1
crystal.ns.cloudflare.com. 2 AAAA 2606:4700:50:0:0:0:a29f:26ca
crystal.ns.cloudflare.com. 2 AAAA 2803:f800:50:0:0:0:6ca2:c2ca
crystal.ns.cloudflare.com. 2 AAAA 2a06:98c1:50:0:0:0:ac40:22ca
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0