1. In a medium bowl, whisk together 2 tablespoons olive oil, lime juice, soy sauce, garlic, cumin, chili powder, smoked paprika, oregano, salt, and pepper.

2. Add the sliced steak to the bowl and toss until every piece is well coated in the marinade. Cover and refrigerate for at least 30 minutes and up to 4 hours.

3. While the steak marinates, slice the bell peppers and onion into thin, even strips so they cook quickly and evenly.

4. When ready to cook, heat a large cast-iron or heavy skillet over medium-high heat until very hot. Add the remaining 1 tablespoon olive oil.

5. Add the marinated steak in a single layer. Let it sear without stirring for 2 to 3 minutes so a crust forms, then cook, stirring occasionally, until the pieces are just cooked through but still tender. Transfer the steak and any juices to a plate and tent with foil.

6. In the same skillet, add the sliced peppers and onion. Season lightly with a pinch of salt and cook, stirring often, until tender-crisp with a few charred edges, about 5 to 7 minutes.

7. Return the steak and its juices to the skillet with the peppers and onions. Toss everything together and cook for 1 to 2 minutes more, just until heated through.

8. While the fajita mixture finishes, warm the tortillas in a dry skillet, in the oven wrapped in foil, or in the microwave wrapped in a damp paper towel until soft and pliable.

9. To serve, fill each warm tortilla with steak and vegetables. Top with sour cream, shredded cheese, cilantro, and avocado slices if using.

10. Finish each fajita with a squeeze of fresh lime juice and serve immediately with extra lime wedges on the side.