Apex domains cannot have CNAME records.
Question and response
Question
dig linux.kolst.it. NS
Answer
linux.kolst.it. 2 NS ns.kpnqwest.it.
linux.kolst.it. 2 NS ns2.kpnqwest.it.
Authority
The response has no authority records.
Additional
ns.kpnqwest.it. 2 A 212.97.32.3
ns2.kpnqwest.it. 2 A 94.141.24.93
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0