1. In a medium bowl whisk together the lime juice, 2 tablespoons olive oil, garlic, cumin, chili powder, smoked paprika, dried oregano, salt, and pepper until well combined.

2. Place the sliced flank steak in a large zip-top bag or shallow dish and pour the marinade over the top, turning to coat all of the pieces evenly. Marinate in the refrigerator for at least 30 minutes and up to 2 hours.

3. Heat the remaining 1 tablespoon olive oil in a large cast-iron or heavy skillet over medium-high heat. Add the sliced bell peppers and onion and cook, stirring occasionally, until tender and lightly charred, about 6 to 8 minutes. Transfer the vegetables to a plate.

4. Return the skillet to high heat. Working in batches if necessary, add the marinated steak in a single layer and sear without moving for 2 to 3 minutes per side, or until nicely browned on the outside but still pink inside. Do not overcrowd the pan.

5. Transfer the cooked steak to a cutting board and let rest for 5 minutes. If the steak was not pre-sliced, slice it now into thin strips against the grain. Toss with any accumulated juices.

6. While the steak rests, warm the tortillas in a dry skillet, wrapped in foil in a low oven, or in the microwave between slightly damp paper towels until soft and pliable.

7. To serve, layer warm tortillas with steak, peppers, and onions. Top with cilantro and a spoonful of sour cream or crema, then finish with a squeeze of fresh lime juice. Serve immediately.