1. Flatten each pork slice to 3/4-inch thickness by pressing it with flat side of a chef's knife. Sprinkle pork slices with salt. Place flour in a shallow dish and dredge pork slices in it.
2. Warm oil in a large skillet over medium-high heat. Working in batches if necessary, cook pork medallions, turning once, until well browned on both sides, about 4 minutes total. Transfer pork to a plate.
3. Add wine and lemon juice to skillet and bring to a boil, scraping up browned bits from bottom of pan with a wooden spoon. Boil, stirring occasionally, until thickened, about 5 minutes. Remove from heat; stir in butter and parsley. Return pork to pan and warm through, turning slices to coat with sauce. Serve immediately.