Bring a large pot of water to a rapid boil and add salt. Slowly add the pasta and stir gently. Return to a boil and cook for 8 to 10 minutes, or until desired tenderness.
While the pasta is cooking, make the spinach pistachio pesto. In a food processor, add the spinach, basil, pistachios, garlic, lemon juice, parmesan cheese, salt, and pepper. Turn the food processor on and slowly stream in the olive oil. Mix until pesto is smooth. Stop the machine and remove the lid. Scrape down the sides with a spatula and mix again if necessary. Taste and adjust seasonings, if necessary. If you want the pesto to be a little thinner, you can add more olive oil.
Reserve 1 cup of the pasta water. Drain the pasta and put it in a large bowl. Add the pesto (start with half of the recipe) and 1/4 cup of the pasta water to the pasta and stir until pasta is well coated. Add additional pesto and pasta water, if necessary, until desired consistency and flavor is reached. Season with salt and pepper, to taste. Garnish with crushed red pepper flakes and parmesan cheese, if desired. Serve warm.