Kitchen converge, Vagrant/Virtualbox and SSL error

I'm trying to setup Vagrant/Virtualbox/kitchen-vagrant on RHEL8. We're behind a corporate proxy.
During kitchen converge, it's getting an error on the Installing cookbook gems step:
STDOUT: Fetching source index from
STDERR: Retrying fetcher due to error (2/4): Bundler::Fetcher::CertificateFailureError Could not verify the SSL certificate
There is a chance you are experiencing a man-in-the-middle attack, but most likely your system doesn't have the CA certificates needed for verification. For information about OpenSSL certificates, see To connect without using SSL, edit your Gemfile sources and change 'https' to 'http'.

I've scoured google and looked at all of the various scenarios where this error happens. I just can't figure out where to put our root certificate so that it gets read, or run the rubygems check.rb script in this context to show me the environment.

Has anyone run across this before? Thanks in advance!