  We present a relativistic heavy-quark action tuning for the charm sector on
ensembles generated by the CLS consortium. We tune a particular 5-parameter
action in an entirely non-perturbative and -- up to the chosen experimental
input -- model-independent way using machine learning and the continuum
experimental charmonium ground-state masses with various quantum numbers. In
the end we are reasonably successful; obtaining a set of simulation parameters
that we then verify produces the expected spectrum. In the future, we will use
this action for finite-volume calculations of hadron-hadron scattering.
