Apex domains cannot have CNAME records.
Question and response
Question
dig osnow.de. NS
Answer
osnow.de. 5 NS ns1.telekom-domains.de.
osnow.de. 5 NS ns2.telekom-domains.de.
Authority
The response has no authority records.
Additional
ns1.telekom-domains.de. 5 A 80.157.195.92
ns2.telekom-domains.de. 5 A 212.185.24.1
ns1.telekom-domains.de. 5 AAAA 2003:2:6:137:80:157:195:92
ns2.telekom-domains.de. 5 AAAA 2003:180:a:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0