Bake the butternut squash on a try with about 1/2 an inch of water in it. Place the squash cut side down and place in the oven at 350 F. for about 1 hour. You should be able to easily pierce a knife through the skin and flesh when it's done. Allow to cool.
Place all ingredients in a blender and blend until smooth.
IMPORTANT: Adjust seasonings to your liking. A lasagna is only as good as it's filling, so make sure this tastes good to you before moving on.
Either pack this in the fridge for up to 2 days, or set aside temporarily to continue prepping your lasagna.
Please note that the nutrition data below is a ballpark figure. Exact data is not possible.