Spray a 9"x13" baking dish with nonstick cooking spray.
Begin your lasagna layers by placing a couple spoonfuls of butternut squash puree in the bottom of the baking dish. Spread to coat bottom of pan evenly.
Next add a layer of the oven-ready lasagna to the dish.
Then add a layer of the sausage and cheese mixture.
Continue pattern of squash, pasta, then sausage/cheese mixture until your pan is full or you run out of the mixtures.
Top with last bit of butternut squash puree, then with shredded cheese, and add bits of fresh sage to the top.
Cover loosely with aluminum foil and bake at 350°F for 25 minutes, covered. Then uncover and bake for 10-15 more minutes until lasagna is bubbling and cheese is getting lightly golden.
Remove from oven. and let rest for 10-15 minutes before eating. Enjoy!