As usual with these types of threads, most people totally disregarded the OP’s clearly stated request of "favorite cover", meaning one, NOT a list. And yes, I know it’s hard to pick just one but I did it. It can be done.
So as not to cause any further upset, I have very carefully limited my nomination to just one, which I’m surprised no one has mentioned: Black Magic Woman by Santana. I’m hoping, though, to avoid being ruthlessly grilled by middlemass or his henchmen, as I would then have to admit I’ve never heard the original.
And shoutout to onhwy61: good one! Yes, some of us do pay attention…