Prepare mashed potatoes according to microwave package directions.
Meanwhile, season chops with salt and pepper. In 12-inch skillet heat oil over medium-high heat. Add pork chops; cook 3 minutes. Turn, add onion. Cook 10 minutes more or until chops are done (160F), turning chops to brown evenly. Stirring onion occasionally. Transfer chops to serving plates.
Add tomatoes and vinaigrette to onion; cook and stir 1 minute more. Serve chops with mashed potatoes. Makes 4 servings.