Apex domains cannot have CNAME records.
Question and response
Question
dig static.orange.es. NS
Answer
static.orange.es. 5 NS dns4.wanadoo.es.
static.orange.es. 5 NS dns1.wanadoo.es.
Authority
The response has no authority records.
Additional
dns1.wanadoo.es. 5 A 62.37.237.140
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0