Prepare the Components
Cook the lasagna noodles according to package directions.
Drain and immediately rinse with cold water to stop the cooking process. Lay noodles flat on baking sheets, placing plastic wrap between layers if you need to stack them, to prevent sticking.
While noodles cook, prepare the filling.
In a large bowl, mash the silken tofu with a fork or potato masher until it resembles ricotta cheese.
Set aside.
Heat the oil in a large skillet over medium heat.
Sauté the diced onion for 5 minutes until translucent.
Add the mushrooms and celery and cook for another 5 minutes, until the vegetables soften and any liquid has evaporated.
Stir in the basil, oregano, salt (if using), and pepper.
Add the cooked vegetable mixture to the mashed tofu and stir until well combined.
To make the cashew cheese, combine the raw cashews, water, nutritional yeast, lemon juice, tamari, onion powder, celery seed, and garlic powder in a high-speed blender.
Blend on high for 1-2 minutes, or until the mixture is completely smooth and creamy.
Assemble and Bake
Preheat your oven to 350°F / 180°C.
Spread 1 cup (240 ml) of tomato sauce evenly over the bottom of a 9 × 13-inch (23 × 33 cm) baking dish.
Arrange a layer of 3 noodles over the sauce.
Top with one-third of the tofu-vegetable mixture.
Spread another cup of tomato sauce over the tofu mixture.
Top with another layer of 3 noodles and a second third of the tofu mixture.
Repeat with the remaining 1 cup (240 ml) of tomato sauce, 3 noodles, and the last of the tofu mixture.
Finish with a final layer of 3 noodles.
Pour the cashew cheese topping over the top layer, spreading it evenly to the edges.
Arrange the fresh tomato slices on top of the cashew cheese.
Bake for 30 to 40 minutes, or until the topping is set and the sauce is bubbling around the edges.
Let it rest for 10 minutes before slicing and serving.
