Mix the oil, chilli powder, cumin, smoked paprika, salt and garlic powder together. Using a brush, brush each side of the mushroom slices with a bit of oil and place on a large baking sheet. Bake in the oven for 20 mins
While the mushrooms are cooking, heat a cast iron skillet to medium high heat.
Add the red pepper and onion to the cast iron pan and cook while turning frequently to prevent burning. The vegetables are ready when they have begun to soften - about 5 minutes.
Arrange the roasted portobellos along with the red peppers and onions on a plate along with the tortillas, or lettuce wraps if you prefer. Top with lettuce, tomatoes, queso fresco, and avocado, etc. Salsa and hot sauce also make excellent additional toppings. Enjoy!