Fill a large pot with water and place over high heat to bring to a boil while you work on the next few steps. (This will be used to cook the pasta in a later step).
In a large sauté pan (or large skillet), cook the bacon until crisp. Remove and place it on a paper-towel-lined plate. Chop or crumble when cooled and set aside for now.
In the same pan, heat the baking grease over medium heat. Add the onion and butternut squash. Cook for 5 minutes, until the onion starts to get tender.
Add the garlic, crushed red pepper, salt, and pepper, and cook for another 1 minute, until fragrant.
Pour the chicken broth into the pan. Continue cooking the squash for about 10-15 minutes over medium heat, uncovered, until the squash is tender. Turn off heat when the squash is tender.
Meanwhile, as the squash is cooking, prepare the pasta. Add the pasta to the pot of boiling water and cook according to package instructions. Reserve ⅔ cup of the pasta water, then drain the pasta into a colander and set aside for now.
In the now-empty pot that the pasta was cooking in, dump in the squash mixture (there should be some broth left in the pan, include this too), the reserved pasta water, and the pumpkin puree. Use an immersion blender to puree into a sauce.
Toss the cooked pasta in the sauce, then portion out and top with the bacon. Enjoy!