C first. C++ was originally a superset of C, though my understanding is that that is no longer strictly the case.
Still, learning C will make it easier to learn C++, because C is far simpler and in order to understand C++ you’ll have to master C’s concepts anyway.
C++ still the superset of a language that is a dialect of C. In terms of ISO, it's probably still closest to the C90 dialect, with some C99-like features (inline functions, // comments).
Nearly everything you learn with C can be applied to C++ (though some may be frowned upon in modern code bases.) So I recommend learning C...
I would agree -- C first. C is foundational knowledge imo.