In a large resealable bag, combine cider vinegar, salt, black pepper, minced garlic, sliced onion, and olive oil.
Mix the marinade ingredients until the salt completely dissolves.
Add lamb chops to the bag and coat thoroughly with the marinade.
Seal the bag and refrigerate for 2 hours, turning occasionally.
Heat a grill pan over medium-high heat.
Remove lamb chops from marinade and discard the used marinade.
Cook chops for 3 1/2 minutes on each side until well seared and cooked to desired doneness.