Apex domains cannot have CNAME records.
Question and response
Question
dig ulteh.es. NS
Answer
ulteh.es. 4 NS elmo.ns.cloudflare.com.
ulteh.es. 4 NS mia.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0