Apex domains cannot have CNAME records.
Question and response
Question
dig free.org. NS
Answer
free.org. 5 NS ns0.free.org.
free.org. 5 NS ns2.free.org.
free.org. 5 NS ns1.free.org.
free.org. 5 NS freens3-scw.free.fr.
Authority
The response has no authority records.
Additional
ns0.free.org. 5 A 213.36.252.136
ns1.free.org. 5 A 213.36.252.197
ns2.free.org. 5 A 213.36.253.23
freens3-scw.free.fr. 5 A 51.159.199.148
ns0.free.org. 5 AAAA 2a01:e0d:1:2:58bf:f988:0:1
ns1.free.org. 5 AAAA 2a01:e0d:1:2:58bf:f9c5:0:1
ns2.free.org. 5 AAAA 2a01:e0d:1:3:58bf:fa17:0:1
freens3-scw.free.fr. 5 AAAA 2001:bc8:1203:102:0:0:0:0
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0