Preheat the oven to 375 F and line a large baking sheet with parchment paper.

Slice the zucchini in half vertically and use a spoon to scoop out the flesh inside the zucchini. Place on the baking sheet and spray with avocado oil spray (or brush with avocado oil). Set aside.

Using a large pan, preheat on medium heat and add the beef, onion, and garlic, and season with Italian seasoning. Crumble the ground beef until browned and the onions are translucent.

Stir in the marinara sauce and simmer for 3-4 minutes. Remove from the heat.

Stuff the zucchini with the beef mixture and sprinkle with cheese (if using). Transfer to the preheated oven and bake for 20-25 minutes or until the zucchini is softened and the filling is bubbly.

Remove from the oven and allow to cool slightly before topping with chopped parsley and serving with a fork and knife.