Apex domains cannot have CNAME records.
Question and response
Question
dig saruman.net. NS
Answer
saruman.net. 5 NS ns1.saruman.net.
saruman.net. 5 NS ns1.elrond.eu.
saruman.net. 5 NS ns1.istari.eu.
saruman.net. 5 NS ns1.elros.eu.
saruman.net. 5 NS ns1.radagast.eu.
Authority
The response has no authority records.
Additional
ns1.elros.eu. 5 A 195.123.227.27
ns1.elrond.eu. 5 A 82.118.22.191
ns1.istari.eu. 5 A 185.75.243.51
ns1.saruman.net. 5 A 107.174.123.206
ns1.radagast.eu. 5 A 89.144.8.165
ns1.elros.eu. 5 AAAA 2a02:27aa:0:0:0:0:0:1252
ns1.elrond.eu. 5 AAAA 2a05:9404:0:0:0:0:0:bef
ns1.istari.eu. 5 AAAA 2a13:9403:0:0:7b77:44d3:5c12:ff53
ns1.saruman.net. 5 AAAA 2607:9d00:2000:7:0:0:1ac6:e7f3
ns1.radagast.eu. 5 AAAA 2a0c:4ac1:4:de:de:de:ff53:ff53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0