Barkeeper's Friend is oxalic acid. It will damage the resin. The care and use manuals from brands that recommend the use of liquid BKF say to use a small amount of a damp cloth, and spread it on the damp cloth before contacting the stone. No manufacturer recommends the powdered BKF that I am aware of.

Hmm, ok - well my bad then. Anything I can do to restore it?

You will need a quartz renew kit with the pro that knows how to use it without doing more damage. Hope Joseph Corlett will swing thru as he is the expert on this type of issue.

Just to clarify though, I didn’t use standard BKF. This is what I used:

Bar Keepers Friend Original Stain Remover Powder 250g https://a.co/d/hZJ9kF7

Which I’ve read is OK for quartz. The surface does not seem damaged, you can just see the sheen is less in the area I treated.

Its best to use the recommended cleaners for your brand quartz countertops. Look at your quartz brand website.

You'll need a Quartz Renew kit. Unfortunately, the darker colors are the most difficult to restore. Probably not a DIY project.

Were I called to this job, you'd acknowledge in writing that the top was ruined and I could only make it better. I'd guess how much replacement would be and charge you half that whether it took me an hour or 6. If you weren't happy, you would not be charged.