1. Heat oven to 400°F (200°C). Halve the spaghetti squash lengthwise, scoop out seeds, brush cut sides with 1 tbsp olive oil, and season with 1/2 tsp salt and 1/4 tsp pepper.

2. Place squash cut side down on a lined baking sheet; roast 35–40 minutes until tender. Cool 5 minutes.

3. Shred the flesh into strands with a fork. Transfer to a colander, sprinkle remaining 1/2 tsp salt, and drain 10 minutes. Gently squeeze out excess moisture.

4. While squash roasts, heat 1 tbsp olive oil in a skillet over medium. Sauté onion 3–4 minutes until translucent. Add garlic and red pepper flakes; cook 30 seconds.

5. Stir in marinara and Italian seasoning; simmer 8–10 minutes. Season with pepper to taste.

6. Lower oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.

7. Spread a thin layer of sauce in the dish. Add half the squash strands, dot with half the ricotta, and sprinkle with 1 cup mozzarella.

8. Repeat with more sauce, remaining squash, remaining ricotta, and 1/2 cup Parmesan mixed with the remaining 1 cup mozzarella.

9. Cover with foil and bake 20 minutes. Uncover and bake 10–15 minutes more until bubbly and golden. Broil 1–2 minutes if desired.

10. Rest 5–10 minutes. Top with chopped basil or parsley and serve warm.