Preheat oven to 350°F and line a rimmed baking sheet with parchment paper. Toss the sliced butternut squash with 2 tablespoons of olive oil and season it with ½ teaspoon sea salt. Spread the squash onto the baking sheet. Use a second baking sheet or layer it if it doesn't all fit. Roast the squash for 30 minutes, until tender. Keep the oven at 350°F after removing the squash.

Heat 1 tablespoon of olive oil in a saucepan over medium-high heat. Add the minced garlic and cook for 30-60 seconds until golden, being careful not to burn it. Reduce the heat and stir in the tomato sauce. It might start to pop, so keep the lid nearby. Add ¼ cup of the nutritional yeast, dried Italian seasoning, and black pepper. Cover the sauce and simmer on medium-low heat as you cook the mushrooms and spinach.

Heat 1 tablespoon of olive oil in a large skillet on medium-high heat. Add the mushrooms and a generous pinch of sea salt, and stir. Cook for 5-8 minutes, stirring the mushrooms periodically, until they release moisture. Add the spinach, tarragon, and rosemary. Stir well, and remove from heat.

Break the tofu up and place it in a food processor. Process until smooth, then add the remaining ½ cup of nutritional yeast, apple cider vinegar, and 1 ½ teaspoons salt. Process again until smooth and season with additional salt to taste.

Coat an 8x8-inch baking dish with olive oil or non-stick cooking spray. Line the bottom of the baking dish with a layer of roasted squash. Spread on ½ cup of tofu "cheese," sprinkle ½ cup of the mushrooms and spinach, and spread on half of the sauce. Repeat the layers in this order until all ingredients have been used.

Place the lasagna in the preheated oven (350°F) and bake for 40 minutes or until golden brown and bubbling around the edges. Let sit at room temperature for 5-10 minutes and enjoy hot!