Place steak in a large resealable plastic bag. Add lime juice, oil, chili powder, salt, and cayenne pepper. Coat steak with marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator, 30 to 60 minutes.
Preheat the oven to 400 degrees F (200 degrees C).
Remove meat from marinade and shake off excess. Discard marinade. Place meat in the center of a (12x18-inch) sheet of heavy-duty aluminum foil. Lift foil sides; double fold top and ends to seal packet, leaving room for heat circulation inside.
Place peppers, onion, and garlic in the center of a (12x18-inch) sheet of heavy-duty aluminum foil. Repeat folding process to seal packet.
Wrap tortillas tightly in heavy-duty aluminum foil.
Bake steak and vegetables in foil packets in the preheated oven until steak reaches desired doneness, 145 degrees F (63 degrees C) for medium-rare, and vegetables are tender, 30 to 35 minutes. Add tortillas to the oven until heated through during the last 10 minutes of baking.
Open packets carefully by cutting along top fold with a sharp knife, allowing steam to escape. Thinly slice steak.
Fill warm tortillas with steak and vegetables. Top with guacamole, salsa, and sour cream.
