Fill a large pot with water, add salt, and bring to a boil. Cook pasta for 8-10 minutes until al dente, then drain and reserve 1 cup of pasta water.

In a food processor, combine spinach, garlic, nuts, Parmesan, and lemon juice. Blend to a coarse paste, adding olive oil until smooth. Season with salt and pepper.

Heat a large skillet over medium heat, add olive oil, then sauté diced bell peppers and vegetables for 5-7 minutes until softened.

In the skillet, add the drained pasta and spinach pesto, mixing until well coated. Use reserved pasta water to adjust consistency.

If using protein, fold it into the pasta mixture and heat gently for 2-3 minutes.

Serve hot or at room temperature, garnished with extra Parmesan and herbs.