01 - In a large bowl, whisk together lime juice, lime zest, olive oil, garlic, chili powder, cumin, smoked paprika, salt, and black pepper. Add 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 cook 6 to 7 minutes per side until cooked through and 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 the cooked chicken to serving plates. If using cheese, sprinkle it over the hot chicken so it melts slightly.
05 - Spoon a generous portion of the avocado mixture over each chicken breast. Garnish with lime wedges and extra cilantro. Serve immediately.