dns.opendns.com has no NS records.
NS records for this zone are defined at opendns.com.
NS records for this zone are defined at opendns.com.
Question and response
Question
dig dns.opendns.com. NS
Answer
The response has no answer records.
Authority
opendns.com. 86400 SOA auth1.opendns.com. noc.opendns.com. 1772234108 16384 2048 1048576 2560
Additional
. 32768 OPT ; payload 4000, xrcode 0, version 0, flags 32768