To answer your initial question, yes Unbound can do what you asked but would normally not be desired.
To do so, create a new config file eg:
sudo nano /etc/unbound/unbound.conf.d/forwarders.conf
With below content:
forward-zone:
name: "."
forward-addr: 8.8.8.8
forward-addr: 8.8.4.4
And restart:
sudo service unbound restart