Apex domains cannot have CNAME records.
Question and response
Question
dig efisens.net. NS
Answer
efisens.net. 5 NS ns-184-a.gandi.net.
efisens.net. 5 NS ns-241-b.gandi.net.
efisens.net. 5 NS ns-249-c.gandi.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0