Apex domains cannot have CNAME records.
Question and response
Question
dig ufinet.com.sv. NS
Answer
ufinet.com.sv. 5 NS ns2.ufinetlatam.net.
ufinet.com.sv. 5 NS ns1.ufinetlatam.net.
Authority
The response has no authority records.
Additional
ns1.ufinetlatam.net. 5 A 167.250.220.220
ns2.ufinetlatam.net. 5 A 186.148.105.105
ns1.ufinetlatam.net. 5 AAAA 2803:e880:8001:220:0:0:0:220
ns2.ufinetlatam.net. 5 AAAA 2803:2b00:8001:105:0:0:0:105
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0