Why not keep it simple with a wine reduction. I’d start with some chopped shallots in olive oil with a pat of butter, maybe some sliced mushrooms and then the wine, with pepper and minimal salt. Maybe some fresh rosemary that you remove before serving for added freshness. You could add fresh basil at the very end for a flavor pop.
Webber’s Way to Grill cookbook has this: Tea-rubbed fillet mignon. It is probably the best steak I have ever grilled - no sauce needed, I am sure you could sear it instead of grilling.
And I lose further credit for it being the only sauce that I find utterly incapable of making myself. I have no idea why I can create Hollandaise blindfolded or any other egg/butter emulsion sauce without any trouble. Yet Bearnaise breaks every time I try to create it.