Apex domains cannot have CNAME records.
Question and response
Question
dig astro4dev.org. NS
Answer
astro4dev.org. 5 NS ns15.worldnic.com.
astro4dev.org. 5 NS ns16.worldnic.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0