Apex domains cannot have CNAME records.
Question and response
Question
dig visp.net. NS
Answer
visp.net. 4 NS ns1.visp.net.
visp.net. 4 NS ns2.visp.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0