Erotica's such a wide field now, it feels like asking for the biggest fish in the ocean—there are whole different schools swimming in different currents. You've got the absolute titans of self-publishing on Amazon like Ruby Dixon, who basically owns the sci-fi romance and monster romance subgenre. Her 'Ice Planet Barbarians' series is a cultural phenomenon that proved there's a massive audience for adventurous, plot-heavy stories with plenty of steam.
Then there's authors like Jessa Kane for super short, high-drama, taboo-adjacent novellas that are pure escapist fantasy, or Sierra Simone who writes these intensely philosophical and religiously-charged erotic romances like 'Priest' that generate endless discussion. But 'bestselling' can also mean those writing more mainstream dark romance or contemporary erotica that tops the charts, like Penelope Douglas or Katee Robert, whose 'Neon Gods' retellings blew up. It's less about a single author ruling the genre and more about which niche is hot at the moment—alien dads were last year, maybe mafia omegas are next.
Honestly, my Kindle Unlimited recommendations are a wild ride these days, and the algorithm pushes new names to the top every week.