Apex domains cannot have CNAME records.
Question and response
Question
dig e-encuesta.com. NS
Answer
e-encuesta.com. 5 NS ns-93.awsdns-11.com.
e-encuesta.com. 5 NS ns-1355.awsdns-41.org.
e-encuesta.com. 5 NS ns-651.awsdns-17.net.
e-encuesta.com. 5 NS ns-1976.awsdns-55.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0