Preheat your pellet smoker to 375 °F.
In a bowl, combine the brown sugar, smoked paprika, poultry seasoning, ancho chile powder, ground cumin, and kosher salt.
Remove the giblets and neck. Dry your turkey well with paper towels.
Cut out the backbone of a cleaned turkey, flip the turkey over and press the breast down to flatten it out.
Trim any excess fat and tuck wing tips under the turkey.
Heavily apply the spice mixture under the skin and over the top of the skin.
Coat grill grate with cooking spray.
Place turkey, skin side up, on the grate. Cover and grill until a thermometer inserted into the thickest portion of thigh registers 160 °F, rotating turkey 90 degrees every 30 minutes. The cooking process will take about 2 1/2 hours.
Place turkey on a cutting board. Tent it under foil for 30 minutes. Remove skin before carving.