Preheat the oven to 375°F.
In a small bowl, combine the ground cumin, smoked paprika, chile powder, garlic powder, and onion powder; set the spice mixture aside.
Season the chicken thighs on both sides with kosher salt and pepper.
Heat an oven-safe large skillet over medium-high heat. Add the olive oil and, once hot, add the seasoned chicken. Brown the chicken about 2 minutes per side.
Cover the skillet (with a lid or foil) and transfer it to the preheated oven. Roast 15–20 minutes, or until the chicken reaches an internal temperature of 165°F.
While the chicken cooks, make the quick pico: in a bowl combine the quartered grape tomatoes, finely diced red onion, chopped cilantro, and the juice of the lime. Season the pico with a pinch of salt and pepper; set aside.
When the chicken is done, remove the skillet from the oven. Transfer the chicken to a cutting board or bowl, keeping the pan and any cooking juices; do not discard the juices.
Shred the chicken with two forks or chop it into small pieces. Add the reserved spice mixture to the shredded chicken and mix until the spices are evenly distributed.
Return the shredded, seasoned chicken to the skillet with the pan juices and warm over medium-low for 1–2 minutes, tossing to coat so the chicken stays moist. Remove from heat.
Divide the 8 ounces of grated cheddar into eight equal portions (1 ounce each). For each taco: heat a clean non-stick skillet over medium-low heat. Sprinkle half of one cheese portion (½ ounce) into the skillet so it starts to melt.
Place one tortilla directly on top of the melting cheese in the skillet. Sprinkle the remaining half of the cheese portion (½ ounce) onto the top of the tortilla.
Add about 1/8 of the shredded chicken to the center of the tortilla, then top with a spoonful of the quick pico. Cook until the cheese on the bottom is golden and crispy and the top cheese has melted, adjusting heat as needed to avoid burning.
Gently fold the tortilla in half, transfer the taco to a plate, and repeat steps 10–12 with the remaining tortillas, cheese, and chicken.
Serve the tacos with any remaining pico and an extra squeeze of lime.