Apex domains cannot have CNAME records.
Question and response
Question
dig billaud.eu. NS
Answer
billaud.eu. 5 NS wapiti.billaud.eu.org.
billaud.eu. 5 NS cricetus.billaud.eu.org.
billaud.eu. 5 NS wombat.billaud.eu.org.
billaud.eu. 5 NS microtus.billaud.eu.org.
Authority
The response has no authority records.
Additional
wombat.billaud.eu.org. 5 A 139.99.155.59
CRICETUS.BILLAUD.EU.ORG. 5 A 51.83.78.12
wombat.billaud.eu.org. 5 AAAA 2402:1f00:8100:400:0:0:0:428
CRICETUS.BILLAUD.EU.ORG. 5 AAAA 2001:41d0:305:2100:0:0:0:643a
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0