Boil the pasta: Bring a large pot of salted water to a boil. Cook the pasta until just shy of al dente, 1–2 minutes less than package directions. Drain and set aside.

Preheat and prep: Heat the oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.

Sauté the aromatics: Warm the olive oil in a large skillet over medium heat. Add the onion and bell pepper with a pinch of salt. Cook 5–6 minutes, until softened. Stir in the zucchini and cook 2–3 minutes more. Add the garlic and cook 30 seconds, until fragrant.

Brown the turkey: Push the veggies to the edges of the skillet and add the ground turkey to the center. Season with salt, black pepper, Italian seasoning, and red pepper flakes if using. Cook, breaking it up with a spoon, until no longer pink and lightly browned, about 5–7 minutes.

Build the sauce: Stir in the tomato paste and cook 1 minute to caramelize slightly. Pour in the marinara and chicken broth. Simmer 3–5 minutes, adjusting salt and pepper to taste. You want a saucy, slightly loose mixture that will coat the pasta.

Combine with pasta and cheese: In a large bowl, mix the drained pasta with the turkey sauce. Fold in 1/3 cup of the Parmesan and 1/2 cup of the mozzarella so it melts into the pasta.

Assemble the bake: Spread the mixture evenly in the prepared baking dish. Top with the remaining mozzarella and sprinkle the remaining Parmesan over the top.

Bake: Place on the center rack and bake 18–22 minutes, until the cheese is melted and bubbly. For extra color, broil 1–2 minutes at the end, watching closely.

Rest and garnish: Let the bake rest 5–10 minutes so it sets. Sprinkle with chopped basil or parsley. Serve warm.