Incorrect DNS information controlled by Group Policy

I was troubleshooting an issue with DNS and set the clients DNS to an external DNS server using group policy (which overrides any local settings). The secondary DNS is an internal DNS sever (the DC), but the clients are not connecting to the domain.

Now, I can’t use gpupdate /force to update the clients and remove this policy because they can’t find the DC.

Obviously, this was a really stupid mistake, but how can I fix it? How can I either manually send an updated group policy to my clients or force the dns client to use the secondary DNS so that it can find the domain?