01 - Whisk together lime juice, lime zest, olive oil, garlic, chili powder, cumin, smoked paprika, salt, and black pepper in a large bowl. Add the chicken breasts and turn to coat evenly. Cover and marinate for at least 20 minutes, or up to 2 hours refrigerated.
02 - Preheat a grill or skillet over medium-high heat. Remove chicken from the marinade and discard excess liquid. Cook 6 to 7 minutes per side until the internal temperature reaches 165°F.
03 - While the chicken cooks, combine diced avocados, tomato, red onion, cilantro, lime juice, and salt in a bowl. Gently toss to combine without mashing the avocado.
04 - Transfer cooked chicken to serving plates. Sprinkle shredded cheese over each breast while hot so it melts slightly, if using.
05 - Spoon generous portions of the avocado mixture over each chicken breast. Garnish with lime wedges and extra cilantro. Serve immediately.