Fill a large pot with water. Add 2 teaspoons salt and bring to a boil. Add pasta and butternut squash. Let water return to a boil, reduce heat to simmer and cook 6 minutes or until pasta is cooked al dente.
Pour 1 cup of pasta water into a glass measuring cup. Set aside. Drain pasta and squash in a large colander and rinse briefly in cold water to prevent pasta from sticking together. Toss with 1 tablespoon of olive oil.
Add remaining oil to the pasta pot and heat over medium heat. Add the leek and sauté until translucent (about 3 minutes). Add the basil, garlic, and lemon peel. Sauté one minute. Add the reserved water and simmer until reduced slightly (about 2 minutes). Add the pasta and squash and toss to coat with the sauce. Add salt and pepper to taste. Toss with pine nuts and cheese. Serve with additional cheese, if desired.