Apex domains cannot have CNAME records.
Question and response
Question
dig openbusiness.com. NS
Answer
openbusiness.com. 5 NS ns3.swisscenter.com.
openbusiness.com. 5 NS ns2.swisscenter.com.
openbusiness.com. 5 NS ns1.swisscenter.com.
openbusiness.com. 5 NS ns4.swisscenter.com.
Authority
The response has no authority records.
Additional
ns1.swisscenter.com. 5 A 83.166.158.200
ns2.swisscenter.com. 5 A 94.103.96.78
ns3.swisscenter.com. 5 A 213.136.91.208
ns4.swisscenter.com. 5 A 46.226.109.118
ns1.swisscenter.com. 5 AAAA 2001:1600:120:100:0:0:0:a
ns2.swisscenter.com. 5 AAAA 2a00:a500:0:93:0:0:0:78
ns3.swisscenter.com. 5 AAAA 2a02:c207:2037:9959:0:0:0:1
ns4.swisscenter.com. 5 AAAA 2001:4b98:dc2:41:216:3eff:fed3:abe0
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0