Toss the boneless skinless chicken thighs or breasts with lime juice, minced garlic, olive oil, cumin, chili powder, oregano, salt, and pepper until evenly coated, with seasoning clinging to the chicken. Marinate for at least 10 minutes at refrigerator temperature or up to 2 hours, so the surface looks glossy and fragrant.

Heat a cast iron skillet over high heat until hot enough that a drop of marinade sizzles immediately. Cook the chicken in a single layer for 4-5 minutes per side until cooked through and lightly charred, turning only once so char spots appear.

As the chicken cooks, break it into smaller pieces with a wooden spoon so the texture becomes tender and shreddable. Continue cooking until the pieces are uniformly cooked with browned edges.

Char the corn tortillas directly over a gas flame or in a dry skillet until you see browned blistered spots. Keep them warm so they stay flexible when filled.

Fill each tortilla with the cooked chicken and top with diced white onion and chopped fresh cilantro. Serve immediately with lime wedges and hot sauce so the toppings stay bright and crisp.