De-stem and chop the portobello mushrooms, then set aside. In a skillet, whisk water, low-sodium soy sauce, nutritional yeast, Worcestershire sauce, garlic powder, and onion powder together. Bring to a boil over high heat. Add onion and mushrooms and reduce heat to medium once boiling. Continue to cook, stirring occasionally, until all liquid has evaporated. Once mushrooms are cooked completely, spoon into tortillas and top with shredded lettuce, diced tomato, and taco sauce as desired.