Preheat the oven to 375°F (190°C).

Cook the pasta according to package instructions until al dente. Drain and set aside.

In a large skillet, heat olive oil over medium heat. Add the chopped onion, bell pepper, and garlic, cooking until softened.

Add the cherry tomatoes and spinach, cooking until the spinach is wilted.

Stir in the cooked pasta, marinara sauce, salt, and pepper. Mix well to combine.

Transfer the pasta mixture to a baking dish.

Sprinkle the grated mozzarella and Parmesan cheese evenly over the top of the pasta.

Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.

Remove from the oven and let cool slightly before serving.