Stabilize your grill at 300 - 325°F, setup for indirect cooking.
Using a pair of kitchen shears or a knife, cut out the backbone then tap the keel bone with the heel of your knife in order to allow the rib charge to fully flatten, just as if you were spatchcocking a whole bird.
To make the Carolina Cajun Butter Injection, melt the butter in a pan and stir in the BBQ Blackening seasoning. You are ready to inject (do not boil the butter). Inject the meat evenly with your melted Cajun Butter. Squirt a bit on the outside of the bird to help the seasoning stick for the next portion of the recipe.
Season the rib cage side first, then season the breast side. Note – for crispy skin, use your fingers to separate the center of the skin from the meat. This space will allow the skin.to roast without soaking up the juice for the breast meat throughout the cook. Make sure to season both the skin and under the skin evenly.
Place the chopped vegetables and rosemary in the bottom of a roasting pan. These vegetables will make a great side dish and will act as a natural roasting rack keeping the bird off the bottom of the rack.
Place the turkey skin side up on top of the vegetables and transfer to the indirect grill.
Cook at 300°F for 45 minutes then check the temp; you should be around an internal temp of 55°F at this point. Give the bird another 45 minutes (11/2 hours total time); you should now we around 125°F. Use this opportunity to turn to the bird, then cook for another 30 minutes. Now you should be at an internal temp of 160°F.
Remove the tray from the grill and take the turkey off the vegetables; allow the bird to rest for 20 minutes. Taste a few of your vegetables and season with the Lane's BBQ rub, then transfer the roasted vegetables to the presentation plate and keep warm.
After the rest, slice the bird however you like, or follow the example provided in the video (a serrated knifeis preferred). Make sure to use your fingers to pick off the meat still connected to the rib cage.
Transfer the slices of turkey to the presentation plate with the roasted vegetables and enjoy!