1. Preheat oven to 350°F. Place fennel seeds, rosemary, salt and pepper in a small food processor or coffee grinder; process until finely ground. Press onto all sides of pork.
2. Melt 4 Tbsp butter over medium heat in a large skillet. Add pork and cook for 10 minutes or until golden brown on all sides. Transfer to a baking dish and place in the oven; cook for 30 minutes or until pork reaches 145°F internally.
3. While pork is cooking, melt remaining butter in same skillet pork was cooked in. Add apples and cook for 10 minutes or until soft, stirring frequently. Stir in remaining ingredients and cook until excess liquid has cooked off. Slice pork thinly and serve with warm apples.
Pork may be coated with fennel mixture several hours ahead and stored covered in the refrigerator until ready to cook.