Heat the oven: Preheat to 400°F (200°C).
Line a baking sheet with parchment for easy cleanup.
Prep the zucchini: Slice each zucchini in half lengthwise. Use a spoon to scoop out the center, leaving about 1/4 inch border all around. Chop about half of the scooped zucchini flesh and set aside; discard any watery or seedy bits.
Season the shells: Place the zucchini halves on the baking sheet.
Lightly brush or spray with olive oil and sprinkle with salt and pepper. This helps them roast and develop flavor.
Sauté the aromatics: Warm the olive oil in a skillet over medium heat. Add onion and bell pepper.
Cook 4–5 minutes until softened. Stir in garlic and the chopped zucchini flesh and cook 1–2 minutes more.
Cook the protein: Add the ground turkey or chicken to the skillet. Break it up and cook until no longer pink, about 5–7 minutes.
If using beans instead of meat, add them after the veggies soften and warm through for 2–3 minutes.
Season and bulk up: Stir in diced tomatoes, quinoa or cauliflower rice (if using), Italian seasoning, smoked paprika, crushed red pepper, and a pinch of salt and black pepper. Simmer 2–3 minutes to reduce excess moisture. Taste and adjust seasoning.
Fill the boats: Spoon the mixture into the zucchini shells, mounding it slightly.
Sprinkle lightly with Parmesan or mozzarella.
Bake: Roast for 15–20 minutes, until the zucchini is tender but not mushy and the cheese is melted and golden in spots.
Finish and serve: Scatter fresh parsley or basil on top. Add a squeeze of lemon for brightness. Serve hot with a simple side salad if you like.