Remove all visible fat from the pork loin and cut it into 8 to 12 slices. Place the pork in a 7 quart Dutch oven and then place the sliced onion, fresh rosemary, diced butternut squash, apples and raisins right on top.
In a large glass measuring cup, add the ingredients for the cooking liquid and mix with a flat whisk until well combined. Add this to the Dutch oven, place the lid on and cook in a 350°F oven for about 75 minutes, or until the squash is really tender.
Remove the lid and continue cooking for an additional 25 to 30 minutes, or until some of the cooking liquid has evaporated and the top starts to turn nicely golden.