Preheat the oven to 375°. Spray a baking sheet with cooking spray and set aside.
Slice the zucchini lengthwise down the middle. Use a melon-baller to carefully scoop the flesh out of the zucchini and transfer to a mini prep food chopper. Pulse several times until the zucchini flesh is finely chopped. Transfer to a bowl.
Add the onions to the food processor and pulse until they are about the size consistency of the zucchini. Transfer to the same bowl as zucchini and add the minced canadian bacon.
Crush the fennel seed either by using a mortar and pestle, a spice grinder, or place a piece of plastic wrap on a cutting board, add the fennel to the center and fold the plastic wrap over it. Use a rolling pin or mallet to crush the fennel seed. Add crushed fennel to the zucchini mixture, along with red pepper flakes, black pepper and salt.
Heat a medium skillet over medium high heat, add the olive oil. When the oil is hot, stir in the zucchini mixture and cook down until it's given up most of it's liquid, about 5-6 minutes. Add the chopped tomato and cook a few minutes more. Remove from heat and set aside.
Tear the bread into small chunks and add them to the food processor along with the parsley. Pulse 3-5 times until coarsely chopped and transfer to the zucchini mixture. Add the mozzarella and basil, stir to combine.
Lightly coat the interior of each zucchini half with a little olive oil. Spoon filling liberally into each zucchini and arrange on a baking sheet. Take a look at the tray and if you see a zucchini leaning in a particular direction -- instead of sitting straight up, prop the zucchini against one of the sides of the sheet pan to hold it erect and prevent it from spilling over in the oven. If most of your zucchini are persnickety - find a shallow casserole dish that will fit them snugly against one another and prevent them from toppling. Drizzle with remaining olive oil and sprinkle with a little mozzarella and parmesan. Bake for 20-25 minutes or until golden. Sprinkle with fresh basil and serve.