Apex domains cannot have CNAME records.
Question and response
Question
dig somvera.cat. NS
Answer
somvera.cat. 5 NS ns2.somvera.cat.
somvera.cat. 5 NS ns1.somvera.cat.
Authority
The response has no authority records.
Additional
ns1.somvera.cat. 5 A 45.15.139.141
ns2.somvera.cat. 5 A 45.15.139.152
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0