Apex domains cannot have CNAME records.
Question and response
Question
dig xelon.ch. NS
Answer
xelon.ch. 3 NS dahlia.ns.cloudflare.com.
xelon.ch. 3 NS beau.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
beau.ns.cloudflare.com. 2 A 108.162.193.73
beau.ns.cloudflare.com. 2 A 172.64.33.73
beau.ns.cloudflare.com. 2 A 173.245.59.73
dahlia.ns.cloudflare.com. 2 A 108.162.192.89
dahlia.ns.cloudflare.com. 2 A 172.64.32.89
dahlia.ns.cloudflare.com. 2 A 173.245.58.89
beau.ns.cloudflare.com. 2 AAAA 2606:4700:58:0:0:0:adf5:3b49
beau.ns.cloudflare.com. 2 AAAA 2803:f800:50:0:0:0:6ca2:c149
beau.ns.cloudflare.com. 2 AAAA 2a06:98c1:50:0:0:0:ac40:2149
dahlia.ns.cloudflare.com. 2 AAAA 2606:4700:50:0:0:0:adf5:3a59
dahlia.ns.cloudflare.com. 2 AAAA 2803:f800:50:0:0:0:6ca2:c059
dahlia.ns.cloudflare.com. 2 AAAA 2a06:98c1:50:0:0:0:ac40:2059
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0