Every time I make this dish, my friends are lining up for seconds!

4 bone-in pork chops
1 tablespoon olive oil
1 teaspoon salt
1/2 teaspoon black pepper
1 tablespoon Worcestershire sauce
2 tablespoons brown sugar
2 tablespoons apple cider vinegar
1 teaspoon garlic powder
1 yellow onion, sliced
1 sprig fresh rosemary or thyme
2 tablespoons salted butter, sliced
1/4 teaspoon red pepper flakes (optional)