Apex domains cannot have CNAME records.
Question and response
Question
dig shell.net.do. NS
Answer
shell.net.do. 4 NS dns3.shell.com.
shell.net.do. 4 NS dns2.shell.com.
shell.net.do. 4 NS dns1.shell.com.
Authority
The response has no authority records.
Additional
dns1.shell.com. 4 A 134.146.80.20
dns2.shell.com. 4 A 144.199.196.20
dns3.shell.com. 4 A 134.163.128.20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0