Step 1: Prepare the Zucchini

1. Preheat your oven to 375°F (190°C).
2. Wash the zucchinis and cut them in half lengthwise.
3. Use a spoon to scoop out the seeds and flesh, leaving about a ¼-inch thick shell. Save the scooped flesh for the filling if desired.

Step 2: Cook the Filling

1. Heat olive oil in a skillet over medium heat.
2. Sauté the onion and garlic until fragrant, about 2 minutes.
3. Add the ground turkey, chicken, or beef (or keep it vegetarian) and cook until browned.
4. Stir in the marinara sauce, Italian seasoning, red pepper flakes, and the reserved zucchini flesh (if using). Let it simmer for 5 minutes.
5. Mix in the cooked quinoa or rice if desired. Season with salt and pepper.

Step 3: Stuff the Zucchini

1. Place the zucchini halves in a baking dish, cut side up.
2. Spoon the filling into each zucchini boat, pressing gently to pack it in.

Step 4: Add the Cheese

1. Sprinkle shredded mozzarella and Parmesan cheese over the stuffed zucchinis.

Step 5: Bake

1. Cover the dish with foil and bake for 25 minutes.
2. Remove the foil and bake for another 10 minutes, or until the zucchini is tender and the cheese is golden and bubbly.