Pat the chops truly dry and season both sides with the salt and pepper. Dry surfaces sear; wet ones steam.
Heat the oil in a wide skillet over medium-high until it shimmers. Sear the chops 3 to 4 minutes a side, until deeply browned and the centers read 140F. Move them to a plate; carryover finishes them at 145F while they rest.
Drop the heat to medium, add the butter, then the onion. Cook 5 minutes, scraping up the pork's browned bits.
Add the apple slices and cook 6 to 8 minutes more, until the apples are tender at the fork with edges catching gold and the onions have gone soft and sweet.
Nestle the chops back in with their resting juices for 1 minute to rewarm.
Serve each chop under a share of the apples and onions and the pan's juices.