Prepare the marinade. In a medium mixing bowl, whisk together olive oil, fresh lime juice, chili powder, cumin, paprika, garlic powder, onion powder, salt, and black pepper. Stir until fully combined and smooth. The lime juice brightens the spices while the oil helps distribute flavor evenly across the chicken.
Marinate the chicken. Add the chicken thighs to the bowl and turn them several times to ensure they are fully coated in the marinade. Cover and let sit for at least 15 minutes at room temperature, or refrigerate for up to 2 hours for deeper flavor development. Longer marinating enhances tenderness and spice penetration.
Preheat your cooking surface. Heat a grill, grill pan, or heavy skillet over medium-high heat. Lightly oil the surface if needed. The pan should be hot before adding the chicken to ensure proper searing and char development.
Cook the chicken. Place the marinated chicken thighs onto the hot surface. Cook for 6 to 7 minutes per side without moving them too frequently, allowing char marks to form. Cook until the internal temperature reaches 165°F and juices run clear.
Rest the chicken. Transfer cooked chicken to a cutting board and allow it to rest for 5 minutes. Resting helps redistribute juices and keeps the meat tender when chopped.
Chop into taco-sized pieces. Using a sharp knife, cut the chicken into small bite-sized pieces suitable for filling tacos evenly.
Warm the tortillas properly. Heat corn tortillas directly over a low flame for a few seconds per side until lightly charred, or warm them in a dry skillet. Warming prevents cracking and improves texture. For authenticity and stability, stack two tortillas per taco.
Assemble the tacos. Place chopped chicken onto the center of each tortilla stack. Top with diced white onion and chopped cilantro. Finish with a fresh squeeze of lime just before serving for bright, authentic flavor.
Serve immediately while warm. For a taco bar presentation, arrange tortillas, chicken, and toppings separately so guests can build their own tacos.