Slice pork into thick rounds. Place in a bowl. Sprinkle with seasonings, then rub in. Melt butter in a large frying pan over medium-high heat. Add pork, then reduce heat to medium. Cook until deep golden, 3 min per side, then remove to a bowl.
Meanwhile, cut potato into large cubes. After pork is removed from pan, pour in juice and water. Using a wooden spoon, scrape up and stir in any brown bits from pan bottom. Add potato. Boil, then cover and reduce heat. Simmer, stirring often until tender, 10 to 12 min. Return pork and any juices back to pan. Cover and simmer, stirring occasionally, until pork is warm, about 2 min. Stir in mint.
Nutrition (per serving)
Lean pork tenderloin and super-nutritious sweet potato produce a substantial dinner.