Apex domains cannot have CNAME records.
Question and response
Question
dig horus.ch. NS
Answer
horus.ch. 5 NS ns2.horus.ch.
horus.ch. 5 NS ns1.horus.ch.
horus.ch. 5 NS ns6.ecoweb.ch.
Authority
The response has no authority records.
Additional
ns1.horus.ch. 5 A 194.182.164.99
ns2.horus.ch. 5 A 185.19.29.61
ns6.ecoweb.ch. 3 A 159.69.1.15
ns1.horus.ch. 5 AAAA 2a04:c44:e00:3eb:482:6cff:fe00:d47
ns6.ecoweb.ch. 3 AAAA 2a01:4f8:1c0c:52e0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0