Butterfly pork loin to become a sheet 1inch thick and about 8 inches by 14 inches. Sprinkle with salt and pepper and set aside.
In a 12 to 14 inch saute pan, heat olive oil until smoking. Add onion and fennel and saute until softened and lightly browned, about 10 minutes. Add ground pork, fennel seeds, pepper,rosemary and garlic and cook until the mixture assumes a light color, stirring constantly, about 10 minutes. Allow to cool. Add chopped fennel leaves and eggs and mix well.
Spread mixture over pork loin and roll up like a jelly roll. Tie with butchers twine and place in roast pan on top of halved red onions. Place in oven and roast 75 minutes, or until interior temperature is 140 degrees F. Remove and allow to rest for 10 minutes. Slice into 1 inch thick pieces and serve with Scafata, recipe follows.