Apex domains cannot have CNAME records.
Question and response
Question
dig koukensheet.com. NS
Answer
koukensheet.com. 5 NS ns2.koukensheet.com.
koukensheet.com. 5 NS ns1.koukensheet.com.
Authority
The response has no authority records.
Additional
ns1.koukensheet.com. 5 A 51.89.195.211
ns2.koukensheet.com. 5 A 51.77.104.26
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0