Apex domains cannot have CNAME records.
Question and response
Question
dig csof.net. NS
Answer
csof.net. 5 NS z.dns.gandi.net.
csof.net. 5 NS ns-128-a.gandi.net.
csof.net. 5 NS ns-158-c.gandi.net.
csof.net. 5 NS ns-223-b.gandi.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0