Preheat your oven to 375°F and soak the raw cashews in hot water for 15 minutes, then drain.
In a high-speed blender or food processor, combine the soaked cashews, firm tofu, nutritional yeast, lemon juice, garlic powder, sea salt, and black pepper, pulsing until a smooth, ricotta-like consistency is achieved.
In a small mixing bowl, stir together the marinara sauce, cooked green lentils, soy crumbles, and dried oregano.
In a small, oven-safe baking dish, spread two tablespoons of the lentil-marinara sauce on the bottom to prevent sticking.
Place a portion of the lasagna noodles over the sauce, followed by a layer of the tofu-cashew ricotta and a handful of fresh spinach.
Repeat the layers of sauce, noodles, and ricotta until all ingredients are used, ending with a layer of sauce and a dollop of ricotta on top.
Cover the dish tightly with foil and bake for 25 minutes; remove the foil and bake for an additional 10 minutes until the edges are bubbling and the top is slightly golden.
Allow the lasagna to rest for 5 minutes before serving to ensure the layers set properly.