Apex domains cannot have CNAME records.
Question and response
Question
dig prolegal.com.mx. NS
Answer
prolegal.com.mx. 5 NS dns.prolegal.com.mx.
Authority
The response has no authority records.
Additional
dns.prolegal.com.mx. 5 A 187.141.163.180
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0