Let the chicken sit on the counter and come to room temperature for about 30 minutes while you preheat the oven and prepare the rest of the ingredients.
Preheat oven to 400°F. Line a large, rimmed baking sheet or a roasting pan with aluminum foil for easy cleanup, if desired.
Pat the chicken very dry with paper towels.
In a small bowl, stir together the brown sugar, chili powder, kosher salt, cumin, smoked paprika, garlic powder, and onion powder.
Rub the seasoning mixture all over both sides of the chicken.
Place the chicken on the prepared pan.
Bake the chicken thighs uncovered for 20-25 minutes, basting with the bbq sauce during the final 5-10 minutes. Remove the chicken from the oven when the juices run clear, and an instant-read thermometer registers 165°F. For a more charred, crispy finish, transfer the chicken to the broiler for a few minutes at the very end. Just keep a close eye on it; the chicken can burn easily.
Allow the chicken to rest for 5-10 minutes before serving. Serve with additional bbq sauce, if desired.