Apex domains cannot have CNAME records.
Question and response
Question
dig leunet.ch. NS
Answer
leunet.ch. 3 NS ns1.leunet.ch.
leunet.ch. 3 NS ns2.leunet.ch.
Authority
The response has no authority records.
Additional
ns1.leunet.ch. 3 A 212.203.32.11
ns2.leunet.ch. 3 A 212.203.33.12
ns1.leunet.ch. 3 AAAA 2a00:aac0:0:1:0:0:0:11
ns2.leunet.ch. 3 AAAA 2a00:aac0:0:2:0:0:0:12
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0