Begin by preheating the oven to 400°F.
With a sharp knife, cut the smaller ends off the acorn squash so it will stand on its side. This will make it easier to cut.
Cut the acorn squash in half lengthwise. Cutting it lengthwise will maintain its shape. Scoop the seeds out with a spoon and discard them. You can also feed them to your chickens like I do.
Line a baking sheet with parchment paper and lay the cut acorn squash cut sides up. I find baking it cut side down is harder to tell if it's tender.
Brush the top of the squash with the olive oil. Sprinkle with ½ tsp salt, and ½ tsp black pepper and roast it in the preheated oven for around 30 minutes until it’s soft and fork tender.
While the squash bakes, dice the onion and apple. Add it to a skillet with 2 cloves of minced garlic, and 1/2 tsp of salt. Sauté over medium-high heat to make caramelized onions and soften the apples.
Add the spicy sausage to the skillet with the vegetables and sauté over medium heat until it’s brown. Once it’s brown remove any excess oil from the sausage mixture and set it aside.
Remove the roasted acorn squash from the oven once they’re done. Scoop the stuffing mixture into the wells of the squash. You can scoop out some of the excess meat of the acorn squash to allow more of the mixture to sit in the squash boats.
Return the stuffed squash to the baking sheet and bake it in the oven for around 10 minutes.
Remove the stuffed squash from the oven and sprinkle the tops with the parmesan cheese. Serve them warm.