Lambert's brown sugar and mustard ribeye recipe?

[girl410]

Anybody have any insight into what is in this recipe? I've experimented with different ratios of light brown sugar, dried mustard powder, salt and pepper, etc and it's close but I think I'm missing a key ingredient or something. Maybe I should be using some type of prepared mustard? Any help appreciated.

I've seen his coffee rubbed brisket recipe is online but haven't found the ribeye recipe anywhere.

Thanks!