Preheat the oven to 275 degrees.

Wrap the tortillas in aluminum foil and heat them in the oven for 20 minutes.

Meanwhile, heat the oil in a large saucepan over medium-high heat. Slice the meat thinly and add it to the oil along with the onion, bell peppers, and mushrooms. Cook and stir until the vegetables are tender and the meat is cooked through. Mix in the fajitas seasoning. Add the water or broth and simmer until the mixture has cooked down a bit, about 5 minutes.

To serve, place the tortillas on a plate and pass the meat mixture, salsa, cheese, sour cream, avocado, and lime in separate bowls.