Saute mushrooms: heat 2 tsp olive oil in 12-inch non-stick skillet over medium-high. Toss mushrooms with chili powder, cumin, salt and pepper (about 3/4 tsp salt 1/2 tsp pepper). Add mushrooms to the heated skillet and saute for about 7 minutes, or until carmelized. Transfer to a medium mixing bowl.
Saute tofu (if using): Using a firm tofu, drain the tofu. Crumble into the skillet with a little onion and garlic, chili powder, cumin, and a little taco mix seasoning. Cook the tofu for about 20 min or until the water dries out. Season with soy sauce and sea salt to taste. Transfer to the bowl with mushrooms.
Saute veggies: heat remaining 2 tsp oil in the same skillet. Add bell pepper and red onion and saute until tender, about 5 minutes. Add the garlic and saute for 1 minute more. Transfer to the bowl with tofu and mushrooms, pour in lime juice and toss.
Butter tortillas: brush top side of tortillas with melted butter.
Wipe the skillet clean with a paper towel and lower the heat to medium.
Toss cheeses together.