In a large bowl, whisk together lime juice, olive oil, minced garlic, cumin, chili powder, smoked paprika, oregano, salt, and black pepper until well combined. Add chicken thighs and toss to coat completely. Cover and refrigerate for at least 30 minutes, or up to 8 hours for deeper flavor.

Heat a lightly oiled skillet or grill pan over medium-high heat. Remove chicken from marinade, letting excess drip off. Cook for 5-7 minutes on the first side without moving until golden brown spots form. Flip and cook another 5-7 minutes until internal temperature reaches 165°F. The chicken should feel firm when pressed and show no pink in the center.

Transfer cooked chicken to a cutting board and let rest for 5 minutes. This keeps the juices in the meat. Then dice or slice the chicken into small, bite-sized pieces.

While chicken rests, warm corn tortillas in a dry skillet over medium heat for 20-30 seconds per side until pliable and slightly toasted with a few char spots.

Fill each tortilla with diced chicken, top with chopped white onion and fresh cilantro. Serve immediately with lime wedges for squeezing over the top.