Apex domains cannot have CNAME records.
Question and response
Question
dig lntelefonesdeportugal.com. NS
Answer
lntelefonesdeportugal.com. 5 NS ns1.lntelefonesdeportugal.com.
lntelefonesdeportugal.com. 5 NS ns2.lntelefonesdeportugal.com.
Authority
The response has no authority records.
Additional
ns1.lntelefonesdeportugal.com. 5 A 148.135.79.242
ns2.lntelefonesdeportugal.com. 5 A 148.135.79.244
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0