Apex domains cannot have CNAME records.
Question and response
Question
dig nic53.net. NS
Answer
nic53.net. 5 NS ns1.nic53.net.
nic53.net. 5 NS ns2.nic53.de.
Authority
The response has no authority records.
Additional
ns1.nic53.net. 5 A 192.174.68.103
ns1.nic53.net. 5 AAAA 2001:67c:1bc:0:0:0:0:103
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0