Apex domains cannot have CNAME records.
Question and response
Question
dig funio.com. NS
Answer
funio.com. 5 NS ns2.io-servers.com.
funio.com. 5 NS ns1.io-servers.com.
Authority
The response has no authority records.
Additional
ns1.io-servers.com. 5 A 174.142.221.7
ns2.io-servers.com. 5 A 184.107.112.7
ns1.io-servers.com. 5 AAAA 2607:f748:1200:11d:174:142:221:7
ns2.io-servers.com. 5 AAAA 2607:f748:1301:0:184:107:112:7
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0