Apex domains cannot have CNAME records.
Question and response
Question
dig cloudheads.eu. NS
Answer
cloudheads.eu. 5 NS dns2.aperture-labs.org.
cloudheads.eu. 5 NS dns.aperture-labs.org.
cloudheads.eu. 5 NS ns0.cloudheads.eu.
Authority
The response has no authority records.
Additional
dns.aperture-labs.org. 5 A 195.191.197.5
ns0.cloudheads.eu. 5 A 193.104.168.148
dns2.aperture-labs.org. 5 A 195.191.196.2
dns.aperture-labs.org. 5 AAAA 2a06:d1c0:dead:1:0:0:0:5
ns0.cloudheads.eu. 5 AAAA 2a06:d1c0:deac:1:0:0:0:148
dns2.aperture-labs.org. 5 AAAA 2a06:d1c0:deae:1:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0