Set Masterbuilt Gravity Series to 450F.
Season turkey legs with barbecue rub or chili powder and grill them hot and fast on all sides but still raw in the middle, about 8-10 minutes.
Separately in a large aluminum tray, add chicken stock, apple cider vinegar, vegetable oil, onions, tomatoes, jalapeños, chipotle peppers, dried chilies, and all dried spices into the vessel. Stir and mix together until well incorporated.
Remove turkey legs and reduce Gravity Series to 300F. Add grilled legs to the braising mixture, making sure the legs are as submerged as possible.
Smoke at 300F for 2 hours, or until the leg meat easily pulls from the bone.
Remove from the Gravity Series and allow the legs too cool until they can be easily worked with.
Pull off the meat from the legs and shred.
Increase Gravity Series to 350F. Strain the braising liquid into a heat-safe pot. Place the pot directly on the grates and reduce liquid by half, about 8-10 minutes.
Pour a small amount of liquid into the shredded turkey and set aside.
Add a cast iron pan or skillet onto your Gravity Series. Dip your corn tortilla into the braising liquid and add directly to the cast iron pan or skillet.
Scatter the entire tortilla with cheese. assemble turkey meat, cilantro, and white onion on one side of the taco. Fold taco over itself.
Crisp on both sides, about 3-5 minutes, and remove from Gravity Series to a plate. Garnish with cilantro and serve immediately with a side of braising liquid for dipping.