Apex domains cannot have CNAME records.
Question and response
Question
dig leyde.org. NS
Answer
leyde.org. 5 NS ns-21.awsdns-02.com.
leyde.org. 5 NS ns-948.awsdns-54.net.
leyde.org. 5 NS ns-715.awsdns-25.net.
leyde.org. 5 NS ns-360.awsdns-45.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0