Preheat oven to 375°F (190°C).
Cook lasagna noodles according to package instructions.
Heat olive oil in skillet over medium heat.
Cook onion, garlic, and mushrooms for 5 minutes.
Stir in lentils, tomato sauce, oregano, basil, salt, and pepper.
Spread thin sauce layer into baking dish.
Layer noodles, mushroom mixture, ricotta, mozzarella repeatedly.
Sprinkle nutritional yeast on top.
Bake 35 minutes until bubbly.
Rest briefly before serving.