Heat a generous amount of olive oil in a large frying pan over medium to high heat. Add the onions and cook until they begin to brown. While the onions cook, slice the zucchini and bell peppers, then add them to the pan. Continue cooking until the vegetables soften and develop some charred edges.

Push the veggies to one side of the pan, add a bit more oil, and place the beef strips in the pan. Cook until nicely browned, adjusting the cooking time if you prefer your beef medium-rare.

Sprinkle Mexican spices or fajita mix over the cooked veggies and beef, stirring to coat everything evenly. Warm the tortillas in a cast-iron skillet, panini press, or microwave until soft, and slightly charred if using direct heat.

Spread salsa or guacamole on each tortilla if using, then top with the beef and veggie mix. Add cheese or nutritional yeast, then roll them up tightly. Serve the wraps warm, ideally right after assembling, to enjoy the freshness and flavors.