Preheat oven to 375°F. Cut squash in half lengthwise, spoon the seeds out and prick randomly with a fork. Place on a baking sheet lined with parchment paper cut side down and bake for 30 minutes.
Preheat large non-stick skillet on low heat and add oil. Add garlic and onion, saute for 4 minutes, stirring occasionally. Add ground turkey and cook for another 7 minutes, breaking into pieces with spatula.
Add cream of mushroom soup, tomato sauce and cornstarch, stir and bring to a boil by raising heat to medium. Reduce heat to low and simmer for 5 minutes or until mixture has thickened a bit.
Reduce oven to 350° F and spray 9" x 13" baking dish with cooking spray. Transfer squash and turkey mixture into the dish, level with spatula, sprinkle with topping and bake uncovered for 35 minutes. Broil on high for 5 minutes or until crust is a bit golden.