In a pot over medium heat, add the onion, garlic and olive oil. Cook until softened, approximately 2 minutes.
Add the oregano, nutritional yeast and salt and cook for an additional minute until fragrant.
Stir in the cremini mushrooms and diced tomatoes and allow to cook down for approximately 2 more minutes. Add the red lentils, broth and tomato sauce at this point.
Bring the sauce to a boil, and then simmer over medium heat for approximately 20 minutes until the lentils are cooked through.
In the meantime, cook pasta according to packaging instructions. Drain the liquid and serve with your lentil bolognese!