The request is oddly specific, which I respect. I’ve come across a fair bit in sapphic erotica and romance that fits. Harper Bliss’s books, particularly some in her 'Perfect Match' series, incorporate power dynamics where discipline or impact play surfaces within a relationship context—think a CEO and her assistant scenario. The scenes are more about the charge of control and surrender than pure punishment, which I find hotter.
If you want something darker and more explicit, 'The Dark Path' series by Luna Lawson has some intense BDSM arcs between female characters. The spanking there isn’t just a brief moment; it’s woven into the dom/sub dynamic and the emotional unraveling of the characters. It’s less 'romantic discipline' and more raw, psychological play.
A classic that often gets overlooked is 'Mistress’s Submission' by J.A. Rock. While not exclusively lesbian, the central F/f relationship features hard scenes that are central to the plot’s exploration of trust and penance. The writing can feel a bit clinical at times, but the intensity is undeniable.
You might also browse the darker corners of Literotica’s sapphic sections—some user-written serials there have incredibly detailed scenes, though quality varies wildly.