UniFi Cloud Gateway Ultra - Let NextDNS overwrite VPN Client DNS?

Hey everyone,

I am using a wireguard VPN client on my UCG Ultra. Together with this I am running the NextDNS CLI. 
My intention was to have the VPN running for privacy & let NextDNS filter everything.

I can’t seem to figure out how to get NextDNS to overwrite the DNS provided by the VPN. Was hoping I could get some help here •ᴗ• 

Thanks for your time in advance!