In a medium bowl, whisk together the olive oil, lime juice, chili powder, cumin, smoked paprika, garlic powder, onion powder, salt, and pepper until smooth.

Cut the chicken thighs into bite-sized pieces, then add them to the bowl. Toss well to coat every piece. Cover and refrigerate for at least 30 minutes, or up to 8 hours for deeper flavor.

Heat a large cast-iron skillet or heavy pan over medium-high heat. Add the marinated chicken in a single layer, working in batches if needed to avoid crowding.

Cook for 4 to 6 minutes per side, until the chicken is cooked through and has nice char marks. Remove from the pan and set aside.

Warm the corn tortillas one at a time in a dry skillet over medium heat, directly over a gas flame, or in a microwave wrapped in a damp towel until soft and pliable.

Place a portion of the cooked chicken on each warm tortilla. Top with a sprinkle of diced onion and fresh cilantro. Serve immediately with lime wedges on the side.