Apex domains cannot have CNAME records.
Question and response
Question
dig adacor.com. NS
Answer
adacor.com. 5 NS ns5.adacor.net.
adacor.com. 5 NS ns.europe.adacor.net.
adacor.com. 5 NS ns.global.adacor.net.
Authority
The response has no authority records.
Additional
ns.europe.adacor.net. 5 A 194.58.196.58
ns.global.adacor.net. 5 A 194.58.198.59
ns5.adacor.net. 5 A 185.42.137.113
ns.europe.adacor.net. 5 AAAA 2a01:3f1:858:0:0:0:0:53
ns.global.adacor.net. 5 AAAA 2a01:3f1:3059:0:0:0:0:53
ns5.adacor.net. 5 AAAA 2a01:3f0:400:0:0:0:0:58
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0