Apex domains cannot have CNAME records.
Question and response
Question
dig mailkit.eu. NS
Answer
mailkit.eu. 2 NS ns3.mailkit.eu.
mailkit.eu. 2 NS ns2.mailkit.eu.
mailkit.eu. 2 NS ns1.mailkit.eu.
mailkit.eu. 2 NS ns4.mailkit.eu.
mailkit.eu. 2 NS ns5.mailkit.eu.
Authority
The response has no authority records.
Additional
ns1.mailkit.eu. 2 A 217.11.236.82
ns2.mailkit.eu. 2 A 185.136.200.18
ns3.mailkit.eu. 2 A 35.245.60.94
ns4.mailkit.eu. 2 A 128.199.136.226
ns5.mailkit.eu. 2 A 103.125.216.244
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0