Apex domains cannot have CNAME records.
Question and response
Question
dig smartrecruiters.app. NS
Answer
smartrecruiters.app. 5 NS ns-955.awsdns-55.net.
smartrecruiters.app. 5 NS ns-1177.awsdns-19.org.
smartrecruiters.app. 5 NS ns-1980.awsdns-55.co.uk.
smartrecruiters.app. 5 NS ns-401.awsdns-50.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0