1. In a medium bowl, whisk together 1/2 cup fresh lime juice, olive oil, minced garlic, cumin, chili powder, smoked paprika, half of the chopped cilantro, salt, and pepper.

2. Place the chicken breasts in a resealable bag or shallow dish and pour the marinade over them, ensuring they are fully coated.

3. Seal or cover and refrigerate for at least 30 minutes, ideally 2–4 hours for deeper flavor.

4. Preheat a grill to medium-high heat, a skillet over medium-high heat, or an oven to 400°F (200°C).

5. Remove chicken from the marinade and discard excess marinade.

6. Cook the chicken for 6–8 minutes per side on the grill or skillet, or bake for 20–25 minutes, until internal temperature reaches 165°F (74°C).

7. Transfer cooked chicken to a cutting board and let it rest for 5–10 minutes.

8. While the chicken rests, gently combine diced avocado, red onion, jalapeño (if using), remaining cilantro, 1 tablespoon fresh lime juice, and a pinch of salt in a bowl.

9. Slice the rested chicken against the grain into strips or cubes.

10. Top the warm chicken generously with the fresh avocado mixture and serve immediately.