Apex domains cannot have CNAME records.
Question and response
Question
dig 1.40.200.in-addr.arpa. NS
Answer
1.40.200.in-addr.arpa. 5 NS ns2.anteldata.com.uy.
1.40.200.in-addr.arpa. 5 NS ns1.anteldata.com.uy.
1.40.200.in-addr.arpa. 5 NS seciu.uy.
Authority
The response has no authority records.
Additional
ns1.anteldata.com.uy. 171705 A 200.40.30.254
ns2.anteldata.com.uy. 171705 A 200.40.220.254
ns1.anteldata.com.uy. 171705 AAAA 2800:a0:53:1001:0:0:0:1
ns2.anteldata.com.uy. 171705 AAAA 2800:a0:53:1002:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0