spf2.authorize.net has no NS records.
NS records for this zone are defined at authorize.net.
NS records for this zone are defined at authorize.net.
Question and response
Question
dig spf2.authorize.net. NS
Answer
The response has no answer records.
Authority
authorize.net. 300 SOA lloyd.ns.cloudflare.com. dns.cloudflare.com. 2019103491 10000 2400 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0