Pat chicken thighs completely dry with paper towels - this is crucial for browning. In a small bowl, mix salt, cumin, garlic powder, and oregano. Season both sides of the chicken evenly, pressing the spices into the meat.

Heat oil in a large cast iron skillet over medium-high heat until shimmering. Add chicken thighs in a single layer without crowding - work in batches if needed. Cook undisturbed for 4-5 minutes until deeply golden and charred in spots. Flip and cook 3-4 minutes more until internal temperature reaches 165°F. Transfer to a cutting board and rest 5 minutes.

Chop the rested chicken into small, bite-sized pieces. Return to the hot skillet over medium-high heat and cook 1-2 minutes, stirring occasionally, until edges get crispy and caramelized. This step makes the difference between good and great street tacos.

Working directly over a gas burner on medium-low, or in a dry skillet, warm each tortilla for 20-30 seconds per side until pliable with light char spots. Stack and wrap in a clean kitchen towel to keep warm.

Pile chicken onto warm tortillas. Top with diced onion and cilantro. Serve immediately with lime wedges and salsa on the side. Let everyone squeeze their own lime - the acid wakes everything up.