For ease, the lasagna can be fully assembled then refrigerated a day in advance.
Start to finish: 1 hour 30 minutes (30 minutes active)
32-ounce tub part-skim ricotta cheese
1 tablespoon chopped fresh rosemary
1 tablespoon chopped fresh thyme
1 tablespoon chopped fresh sage
1 tablespoon chopped fresh marjoram
1 teaspoon salt
1 teaspoon ground black pepper
11/2 pounds butternut squash, peeled
3 Granny Smith or Golden Delicious apples, peeled, cored and finely chopped
1 cup unsweetened apple sauce
3/4 cup water
9-ounce package no-boil lasagna noodles
3 cups baby spinach
1 pound (about 5 cups) shredded fontina cheese
Heat the oven to 400 degrees. Lightly coat a 9-by-13-inch baking pan with cooking spray.
In a medium bowl, whisk together the ricotta cheese, rosemary, thyme, sage, marjoram, eggs, salt and pepper. Set aside.
Bring a large pot of water to a boil. Slice the butternut squash into very thin and even strips. If possible, use a mandoline, if available. Add the squash to the boiling water and blanch for 2 minutes. Use a slotted spoon to transfer the squash to a clean kitchen towel to drain.
In a medium bowl, mix the apples with the apple sauce.
Pour the water into the prepared pan. Top with a layer of lasagna noodles. Spread 1 cup of the ricotta mixture over the noodles. Top with 1 cup of spinach, an even layer of sliced squash, 1/2 cup of the apple mixture and 1 cup of shredded fontina. Repeat this layering 3 more times, skipping the apple in the final layer and ending with a final layer of squash and the final cup of fontina.
Cover the lasagna with foil and bake for 45 minutes. Remove the foil and bake for another 15 minutes, or until the cheese on the top is golden and bubbly.
Allow the lasagna to cool and set up for at least 30 minutes before serving.