Preheat the oven to 350F and lightly oil a 2.5 or 3 quart rectangular casserole dish.
Trim and cut the eggplant into 1-inch cubes. Place it into a colander. Sprinkle it generously with salt, then allow it to sit for 25 minutes. Rinse the eggplant well, then pat it dry firmly.
To make the ricotta, place the cashews, lemon juice, and two tablespoons water in a food processor fitted with the S blade. Process the mixture for about a minute, stopping once to scrape the bowl down. When the cashews have been broken down (they don't have to look smooth at all, just ground up), add the tofu, nutritional yeast, salt, and pepper. Continue processing for 2-3 full minutes, a few times to scrape the processor bowl down. Stop when the mixture is smooth and resembles something like ricotta, only thicker. Add an extra tablespoon water if needed to achieve a creamy consistency. Set the ricotta aside.
Bring a large pot of salted water to boil and cook the pasta according to package instructions, till it's al dente. Drain.
While the pasta cooks, heat the olive oil in a large deep skillet over medium high heat. Add the eggplant. Allow it to sizzle for 4-5 minutes, until it's just starting to brown. Reduce the heat to medium low. Continue cooking the eggplant for 8 (or so) more minutes, until it's meltingly tender. If it's not cooking quickly enough, try covering the skillet for a minute or two.
When the eggplant is cooked, add the pasta and marinara sauce to the skillet. Mix and heat everything through.
Layer a third of the pasta mixture into your casserole dish. Dot this with a third of the ricotta, using a knife to spread the ricotta around a bit. Cover this with another third of the pasta and ricotta. Finish with a layer of pasta and lightly dot the top with the remaining ricotta. Transfer the casserole to the oven and bake for 30-35 minutes, or until hot and bubbly. Serve.