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

In a large skillet, heat the olive oil over medium heat. Add the sliced chicken sausage and cook until browned, about 5-7 minutes.

Add the diced onion and bell pepper to the skillet. Sauté for about 3-4 minutes until the vegetables are softened.

Stir in the minced garlic and cook for an additional minute until fragrant.

Pour in the diced tomatoes with their juice, and add the Italian seasoning, salt, and pepper. Bring to a simmer and cook for 5 minutes.

Add the cooked penne pasta and chopped spinach to the skillet. Toss everything together until the spinach wilts and everything is well combined.

Remove from heat and stir in the grated Parmesan cheese until melted and creamy.

Serve warm, garnished with fresh basil if desired.