Marinate the steak and veggies. Combine olive oil, lime juice, chili powder, ground cumin, cayenne pepper, salt, black pepper, and minced garlic in a jar. Shake well to mix. Divide the marinade between the steak and vegetables, reserving some for cooking. Refrigerate for 1 hour to overnight.

Cook the veggies. In a large skillet over medium-high heat, sauté the peppers and onions until tender-crisp, about 5 minutes. Remove from skillet and set aside.

Cook the steak. In the same skillet, add the marinated steak strips and cook until done, about 7-10 minutes. Return the veggies to the skillet, pour in the reserved marinade, and heat through.

Assemble and serve. Warm the tortillas and serve the steak and veggies with optional toppings like sour cream, guacamole, and salsa.