In a medium bowl, combine lime juice, lime zest, minced garlic, cilantro, cumin, chili powder, smoked paprika, salt, and pepper to create a marinade.
Add the chicken thighs to the marinade, ensuring they are well coated. Cover and refrigerate for at least 30 minutes (up to 2 hours for more flavor).
Preheat a grill or skillet over medium-high heat. Remove chicken from marinade and discard any leftover marinade.
Cook the chicken for about 5-7 minutes per side, or until fully cooked through and no longer pink in the center (internal temperature should reach 165°F / 75°C).
Remove from heat and let the chicken rest for a few minutes before slicing it into strips.
Warm the tortillas in a dry skillet for about 30 seconds on each side or until pliable.
Assemble the tacos by placing a few strips of chicken onto each tortilla. Top with sliced avocado, diced red onion, and a dollop of sour cream or Greek yogurt.
Garnish with fresh cilantro, and add any additional toppings like diced tomatoes or jalapeños if desired.
Notes
Marinate the chicken for longer for enhanced flavor.