Apex domains cannot have CNAME records.
Question and response
Question
dig ipacct.de. NS
Answer
ipacct.de. 5 NS ns.ipacct.de.
ipacct.de. 5 NS ns.ipacct.in.
ipacct.de. 5 NS ns.ipacct.eu.
ipacct.de. 5 NS ns.ipacct.bg.
ipacct.de. 5 NS ns.ipacct.us.
ipacct.de. 5 NS ns.ipacct.ru.
ipacct.de. 5 NS ns.ipacct.jp.
Authority
The response has no authority records.
Additional
ns.ipacct.de. 5 A 152.53.22.215
ns.ipacct.de. 5 AAAA 2a03:4000:6c:30f:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0