Apex domains cannot have CNAME records.
Question and response
Question
dig tabdigital.host. NS
Answer
tabdigital.host. 5 NS alex.tabdigital.eu.
tabdigital.host. 5 NS jerry.tabdigital.eu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0