Apex domains cannot have CNAME records.
Question and response
Question
dig telecomitalia.sm. NS
Answer
telecomitalia.sm. 5 NS dns.omniway.sm.
telecomitalia.sm. 5 NS dns.intelcom.sm.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0