PDNS90.ULTRADNS.com has no NS records.
NS records for this zone are defined at ULTRADNS.com.
NS records for this zone are defined at ULTRADNS.com.
Question and response
Question
dig PDNS90.ULTRADNS.com. NS
Answer
The response has no answer records.
Authority
ultradns.com. 60 SOA pdns196.ultradns.net. domains.vercara.com. 2017038240 10800 3600 86400 60
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0