Preheat oven to 375°F. Prepare a baking sheet by coating with nonstick cooking spray.
Halve zucchini lengthwise, then using a melon baller or small spoon, remove the center of each half — being careful not to remove too much or cut too close to the edge — to create a long channel. Dice the removed zucchini meat and set aside.
Place the zucchini halves hollowed-out side down on the prepared baking sheet and bake for 15 minutes.
Meanwhile, heat oil in a large skillet over medium heat and add the zucchini meat, onion, ground turkey and salt. Cook, stirring often to break up the turkey, until most of the liquid evaporates, about 10 minutes, then add the tomatoes and dressing, and cook for another 5 minutes.
Carefully flip over the baked zucchini halves and spoon heaping piles of the filling into the hollowed-out channels. Evenly sprinkle mozzarella on top of each half and bake for another 20 minutes; serve immediately.
For safe meat preparation, reference the USDA website.
For dips, make and enjoy your dip creation. Then, refrigerate within 2 hours or discard.