Slice the squash. Preheat your oven to 400°F (200°C). Slice the butternut squash in half with a very sharp knife. You can also cut the ends off and microwave it for 2 minutes, to make it easier to slice in half lengthwise.
Prep the squash. Scoop the seeds out of the butternut squash with a spoon. Then, lightly oil the butternut squash and season with salt and pepper.
Bake the squash. Lay the butternut squash, cut side down on a small baking sheet or baking dish, and bake for 40 to 45 minutes.
Cook the sausage and veggies. While the butternut squash is cooking, add the sausage to a saute pan on medium heat. Use a spatula to break up the sausage, and cook until it's just browned. Then, add the onions, garlic, and baby spinach to the pan and stir for 2 to 3 minutes, until the spinach is wilted.
Add the rest. Add the apple, sage, and rosemary and cook for another 2 to 3 minutes, or until the apple has softened slightly. Then turn off the heat and stir in the cranberries and pecans.
Remove the flesh. When the butternut squash halves are cooked through, remove them from the oven, flip them over and remove some of the flesh (but leave plenty to enjoy) to make room for the filling. Save this removed flesh and turn it into mashed butternut squash to enjoy later!
Stuff the squash. Fill the butternut squash with the apple sausage filling. Then turn the top broiler in the oven and bake the filled butternut squash for 5 minutes, or until they're golden on top.