Apex domains cannot have CNAME records.
Question and response
Question
dig com.do. NS
Answer
com.do. 5 NS phloem.uoregon.edu.
com.do. 5 NS ns4.nic.do.
com.do. 5 NS ns5.nic.do.
com.do. 5 NS ns.nic.do.
com.do. 5 NS ns2.nic.do.
com.do. 5 NS a.lactld.org.
com.do. 5 NS ns1.nic.do.
Authority
The response has no authority records.
Additional
a.lactld.org. 4 A 200.0.68.10
ns.nic.do. 171452 A 190.113.72.177
ns1.nic.do. 166230 A 190.113.72.178
ns2.nic.do. 73239 A 190.113.65.12
ns4.nic.do. 166230 A 204.61.216.124
ns5.nic.do. 171452 A 190.113.65.13
phloem.uoregon.edu. 5 A 128.223.32.35
a.lactld.org. 4 AAAA 2801:14:a000:0:0:0:0:10
ns.nic.do. 171452 AAAA 2001:13e0:85d0:106:0:0:0:177
ns1.nic.do. 166230 AAAA 2001:13e0:85d0:106:0:0:0:178
ns2.nic.do. 73239 AAAA 2001:13e0:0:1:0:0:0:12
ns4.nic.do. 166230 AAAA 2001:500:14:6124:ad:0:0:1
ns5.nic.do. 171452 AAAA 2001:13e0:0:1:0:0:0:13
phloem.uoregon.edu. 5 AAAA 2001:468:d01:20:0:0:80df:2023
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0