Melt butter in 12-inch skillet until sizzling; add pork chops. Cook over medium-high heat, turning once, 8-10 minutes or until browned. Season with salt and pepper. Remove chops to serving platter. Keep warm.

Place onions in skillet with pan juices; sprinkle with rosemary. Cook over medium heat, stirring occasionally, 8-10 minutes or until onions are caramelized. Stir in garlic; continue cooking 2-3 minutes or until garlic is softened.

Return chops to pan; continue cooking 4-5 minutes or until pork reaches at least 145°F and is no longer pink.