Apex domains cannot have CNAME records.
Question and response
Question
dig suse.de. NS
Answer
suse.de. 3 NS ns-423.awsdns-52.com.
suse.de. 3 NS ns-792.awsdns-35.net.
suse.de. 3 NS ns-1130.awsdns-13.org.
suse.de. 3 NS ns-1790.awsdns-31.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0