Apex domains cannot have CNAME records.
Question and response
Question
dig surf.net. NS
Answer
surf.net. 4 NS ns1.zurich.surf.net.
surf.net. 4 NS ns3.surfnet.nl.
surf.net. 4 NS ns0.ja.net.
surf.net. 4 NS ns1.surfnet.nl.
surf.net. 4 NS ns2.surfnet.nl.
Authority
The response has no authority records.
Additional
ns0.ja.net. 1 A 128.86.1.20
ns0.ja.net. 1 A 193.63.94.20
ns1.zurich.surf.net. 4 A 195.176.255.9
ns1.surfnet.nl. 1 A 192.87.106.101
ns2.surfnet.nl. 1 A 192.87.36.2
ns3.surfnet.nl. 1 A 195.169.124.71
ns0.ja.net. 1 AAAA 2001:630:0:8:0:0:0:14
ns0.ja.net. 1 AAAA 2001:630:0:9:0:0:0:14
ns1.zurich.surf.net. 4 AAAA 2001:620:0:9:0:0:0:1103
ns1.surfnet.nl. 1 AAAA 2001:610:1:800a:192:87:106:101
ns2.surfnet.nl. 1 AAAA 2001:610:3:200a:192:87:36:2
ns3.surfnet.nl. 1 AAAA 2001:610:0:800c:195:169:124:71
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0