Pre-heat the oven to 450 degrees. You’ll need a large, unlined sheet pan to roast the squashes.
Butter the flesh of the squash halves, and then sprinkle each half with sea salt and pepper. Place the squash halves flesh side down on the sheet pan and roast at 450 degrees for 30 minutes. This will caramelize the outside of the flesh, and steam the squash on the inside to get soft and cooked. While the squash is roasting, you can make the filling.
Melt the butter in a large skillet over medium heat. Add the onions with a pinch of sea salt and cook for a good 5-7 minutes, stirring occasionally, until the onions are getting some caramel color.
Add the cauliflower and apple with a pinch of sea salt, and stir to combine. Cook this over medium high heat for another 7-10 minutes until the veggies and apples are soft and caramelizing.
Add the cinnamon, thyme, nutmeg, red pepper flakes, and garlic, and stir to combine. Cook on medium high for 1 minute until fragrant.
Add the sausage to the skillet to brown. Mix the sausage right into the caramelized veggies and apples for optimum flavor.
Once the sausage is cooked through and browned, stir in the spinach and vinegar. Cook this for about 1 minute until the spinach wilts into the filling.
Once the squash has roasted for 30 minutes. Turn the squashes over to flesh side up, and roast for another 10 minutes until the flesh is very soft.
When the squash is done roasting, fill each squash cavity with the sausage and apple filling.
To make the topping, pulse the topping ingredients a few times in a food processor or blender, and then sprinkle over the top of the stuffed squashes.
Place the stuffed squashes under the broiler in your oven for 2-4 minutes. Broiler intensities can vary from oven to oven, so start checking for doneness around the 2 minute mark. Look for a golden brown crust to the topping.
Scoop the stuffed squashes, digging down into the squash flesh so that each serving has squash. My 2 teenagers can eat an entire half of a squash with the filling, so a lot of times they just take a half squash right onto their plate!