In a saucepan, saute sliced leeks in extra virgin olive oil over medium-low heat for about 5 minutes.
Add butternut squash to pan with your leeks and saute on medium-high heat for 5 minutes, along with your red pepper flakes. Add vegetable stock to pan and bring to a boil. Boil gently for 10 minutes or until the squash is soft and able to mashed down a bit. While everything comes together, heat salted pasta water in a large pan.
Add Barilla Red Lentil Rotini to pan and cook for 7 minutes. Reserve some hot pasta water in case you need to thin out your sauce. While the pasta is cooking, continue to cook the butternut squash and incorporate into a thicker sauce.
When pasta is cooked and drained, add it to your butternut squash pan and incorporate everything together. Taste one last time and season if necessary. Enjoy!