Apex domains cannot have CNAME records.
Question and response
Question
dig flx.com.pe. NS
Answer
flx.com.pe. 5 NS ns2.fiberluxperu.com.
flx.com.pe. 5 NS ns1.flx.com.pe.
flx.com.pe. 5 NS ns1.fiberluxperu.com.
flx.com.pe. 5 NS ns2.flx.com.pe.
Authority
The response has no authority records.
Additional
ns1.flx.com.pe. 5 A 181.224.227.2
ns1.fiberluxperu.com. 5 A 181.224.227.2
ns2.flx.com.pe. 5 A 107.21.139.161
ns2.FIBERLUXPERU.COM. 5 A 107.21.139.161
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0