Preheat the oven to 350 degrees.
In a medium-sized skillet, heat the olive oil over medium heat. Sauté the onions and garlic until the onions start to soften, about 2 minutes. Add the spinach and stir until wilted. Season with basil, thyme, and herbes de provence.
Pour this mixture into a medium-sized mixing bowl. Add the nutritional yeast and tofu. (The tofu will crumble easily to resemble ricotta. The nutritional yeast will add some thickness and a cheesy flavor.)
In a 9-by-13-inch pan, spread the tomato sauce along the bottom. Place a layer of noodles on top. Spread the filling thinly and evenly on top of the noodles. Repeat 2 times, or until the ingredients are used up. Sprinkle the mozzarella “cheese” on top.
Cover with foil and place in the oven for 30 minutes. Uncover and cook for another 15 minutes, or until the “cheese” starts to brown. Remove from the oven and serve immediately.