Place the salmon in a zip top bag or small Briner Bucket. Mix the Oakridge BBQ Game Changer Brine powder with water, according to the instructions on the bag. Make enough brine to fully submerge the salmon. Let the salmon brine for one hour in the refrigerator.
Remove the salmon from the brine a place on the soaked cedar plank. Portion the salmon into four (or more) equal servings, making a cut from the top of the flesh down to the skin, without cutting through the skin. This will allow the fillet to cook as one piece, but makes serving the portions much easier. Next, season the flesh with Killer Hogs BBQ The AP Rub, and then the brown sugar. Then, place the rosemary sprigs down into the cuts you made to divide the portions. Last, top the fillet with the lemon slices.
Grill over indirect heat until the internal temperature reaches 140ºF in the thickest part of the fillet. Remove from cooker, and discard lemon slices and rosemary before serving.