Place prepared squash cut side down, on a baking sheet lined with foil
Put in 375 degree F preheated oven for 30-40 minutes (or until fork tender)
While the squash is roasting, heat a skillet over medium heat and add 1-2 T. olive oil
Add chopped red onion and minced garlic, cook for 2-3 minutes until they become translucent
Add corn kernels and cook for another 3-4 minutes until they start to become tender
Stir in chopped spinach and cook for an additional 2-3 minutes until wilted
Remove from heat and stir in the halved cherry tomatoes, shredded mozzarella, grated Parmesan, fresh basil, and fresh parsley, season with salt and pepper to taste
When acorn squash halves are done roasting, flip them over so the cut side is facing up
Carefully spoon the spinach, corn, and tomato filling into each squash half, packing it down gently
Sprinkle shredded cheese on top of the filling
Return the stuffed squash to the oven, bake for an additional 15-20 minutes, or until the filling is heated through, and the cheese on top is melted and slightly golden
Carefully remove the stuffed squash from the oven and let cool for a few minutes before serving
Garnish with additional fresh herbs, if desired