4 3/4-inch-thick bone-in pork loin chops (1-3/4 to 2 lb.)
1/4 cup extra-virgin olive oil
1 Tbs. chopped fresh thyme
Kosher salt and freshly ground black pepper
1-1/2 lb. red onions (about 3 medium), peeled and cut into 1/4- to 1/2-inch-thick disks
1/2 cup red wine vinegar
1 Tbs. granulated sugar
Prepare a medium-high fire on a gas or charcoal grill. In a medium bowl, toss the pork chops with 1 Tbs. of the oil, half of the thyme, 1 tsp. salt, and 1/2 tsp. pepper. Put the onions on a large plate and sprinkle with 2 Tbs. of the oil and 1-1/2 tsp. salt. In a small bowl, whisk the vinegar, sugar, and the remaining thyme.
Grill the onions, covered, flipping once, until crisp-tender, 5 to 6 minutes per side. Return to the plate. Grill the pork, covered, flipping once, until firm to the touch and just cooked through, 3 to 4 minutes per side.
Transfer the pork to a large platter, brush with some of the vinegar mixture and tent loosely with foil. Heat the remaining 1 Tbs. oil in a large skillet over medium-high heat until itís shimmering hot. Add the onions and the remaining vinegar mixture and cook, stirring, until they absorb all of the liquid and take on a browned, glazed appearance, 3 to 4 minutes. Serve the pork chops with the onions.