In a large skillet on low heat, cook the onion, mushrooms, garlic, salt, and pepper in the olive oil until the onions are caramelized and mushrooms are browned, approximately 8-10 minutes.
In the food processor, puree together the white beans, nutritional yeast, lemon juice, and cumin.
Spread the bean mixture on 3 of the tortillas. Then spread the onion and mushrooms over the beans. Add a layer of tomatoes and then a thin layer plant-based cheese. Cover with the remaining tortillas.
In a clean skillet over low heat, warm the tortillas until heated thoroughly and the cheese has melted.