Preheat the oven to 375 degrees F.
Cook lasagna noodles according to the package instructions.
While the pasta is cooking, thaw the frozen spinach in a small saute pan. Sprinkle with salt and pepper until the spinach is completely thawed. Transfer the spinach to a colander and press out as much water as possible. Set aside.
Meanwhile, prep the ricotta and squash (if making from scratch). Follow the recipe below this one to make your ricotta. Butternut squash can be cooked using this method or used from a can.
Once the noodles have finished cooking, line the bottom of a 9" x 13" with a thin layer of tomato sauce. Add a layer of noodles, 1/2 cup of butternut squash and some dollops of tofu ricotta. Spread evenly across the noodles. Top with some spinach and about 1/4 cup of tomato sauce and again spread evenly across the layer.
Repeat this step for another two or three layers (depending on the size of your pan and noodles).
Top with a final layer of noodles, spread with sauce and sprinkle with the shredded vegan cheese.
Bake in the center of the oven for about 35 - 45 minutes, until the cheese has melted and the lasagna is fully cooked and heated through.
Cool for about 10 minutes, then slice and serve immediately. Garnish with red pepper flakes and some fresh herbs if desired!