Step 1
Preheat oven to 400 degrees F (200 degrees C).
Step 2
Melt butter in a skillet over medium-high heat. Add 1/2 cup sage. Cook and stir until leaves are slightly crisp about 1 minute. Remove leaves with a slotted spoon and drain on paper towels. Cool wrap in paper towels and seal in a plastic bag. Set aside. Reserve the butter.
Step 3
Mix the pepper and cumin in a small bowl. Rinse roast and pat dry; rub evenly with the pepper and cumin. Tuck remaining 1/2 cup sage leaves under the strings on the smooth (fattiest) side of the roast. Set the pork herb side up on a rack in a roasting pan.
Step 4
Spread olive oil in the bottom of a medium baking dish. Thickly slice fennel and place in the dish. Toss to coat with the olive oil and drizzle with 3/4 cup orange juice. Place onions in the dish cut side down.
Step 5
Place roast on the center rack in the preheated oven. Place fennel and onions on lower rack. Bake the pork and vegetables 1 hour or until pork reaches a minimum internal temperature of 145 degrees F (63 degrees C) and vegetables are tender. Turn fennel once during bake time. Reserving drippings transfer meat to a platter and keep warm; let stand at least 10 minutes. Keep the vegetables warm in the baking dish.
Step 6
Place the roasting pan with reserved drippings over high heat on the stove top and mix in the reserved butter from Step 1 the remaining 3/4 cup orange juice stock and vinegar. Bring to a boil and stir to scrape up any browned bits in the pan. Cook stirring often 10 minutes or until reduced by about 1/2.
Step 7
Arrange onions and fennel around the pork. Garnish with fennel tops sprinkle with the fried sage leaves and season with salt to serve.