Apex domains cannot have CNAME records.
Question and response
Question
dig gelbalder.org. NS
Answer
gelbalder.org. 4 NS ns-1840.awsdns-38.co.uk.
gelbalder.org. 4 NS ns-341.awsdns-42.com.
gelbalder.org. 4 NS ns-229.awsdns-28.com.
gelbalder.org. 4 NS ns-1340.awsdns-39.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0