Plan ahead! This recipe requires overnight time. Butterfly the pork loin, if not already, to 1 inch thickness. Cover and refrigerate until ready for use.
Heat the butter and onions in a pan; sauté until golden brown. Combine cooked onions and pecans in a mixing bowl. Stir in the maple syrup, ketchup, vinegar, lemon juice, lemon zest, olive oil, Traeger Chicken Rub and hot pepper sauce. Refrigerate mixture overnight.
Drain pecans and onions through a sieve into a bowl; set sauce mixture aside and reserve. Place drained pecan-onion mixture into a bowl and set aside.
Remove the pork loin from the fridge. Unroll so that it lies flat. Lightly season the inside of the pork with the Pork & Poultry Rub. Arrange the drained pecan-onion mixture down the middle of the loin. Roll up loin and tie with kitchen twine. Season the outside with the Pork and Poultry Rub.
When ready to cook, start the Traeger on Smoke with the lid open until a fire is established (4-5 minutes). Turn temperature to 275 degrees F and preheat, lid closed, for 10 to 15 minutes. .
Place loin on grill and cook for 1 1/2 hours.
Switch the setting to Smoke and continue cooking for 1 1/2 hours or until the internal temperature reaches 145 degrees F on a instant-read thermometer. Mop the loin with the reserved sauce mixture every 20 minutes. Remove from the grill and let rest for 10 minutes before slicing and serving. Enjoy!