Apex domains cannot have CNAME records.
Question and response
Question
dig gsnet.ch. NS
Answer
gsnet.ch. 5 NS ns2.flashcable.ch.
gsnet.ch. 5 NS ns1.flashcable.ch.
Authority
The response has no authority records.
Additional
ns1.flashcable.ch. 5 A 81.92.97.18
ns2.flashcable.ch. 5 A 81.92.97.19
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0