Apex domains cannot have CNAME records.
Question and response
Question
dig snowdns.de. NS
Answer
snowdns.de. 5 NS karl.ns.cloudflare.com.
snowdns.de. 5 NS brianna.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0