Preheat your Yoder Smokers YS640 pellet grill to 225ºF. Trim to remove any silver skin and/or excess fat on the outside of the steak. Rub a small amount of oil on the surface of the meat to use as a binder. Season the steak generously with Cattleman’s Grill Tri-tip Seasoning. Flip the steak and repeat the seasoning process. Rest the meat a few minutes to allow the rub to properly adhere.
Place the ribeye in the center of the second shelf. Smoke until the internal temperature reaches 110ºF-115ºF.
While the steak is smoking, prepare the Century Sauce. Combine the ingredients for the sauce in a small bowl and mix well to incorporate. Set aside.
Next, make the crispy red onion straws. Place the thin sliced onions in a bowl and pour the buttermilk over the onions to cover. Soak for 20-30 minutes. Mix together the flour and Cattleman’s Grill Steakhouse seasoning in a shallow container (casserole dish). Pull a handful of the sliced onions out of the buttermilk, dredge in the seasoned flour and transfer to a cooling rack. Pour the oil into a Lodge 12” cast iron skillet to a depth of about 1/2”. Heat the oil to 375ºF. Fry the onions, turning as necessary to evenly brown on all sides. Remove from oil and place back on the cooling rack.
To make the sweet potato puree, scoop the flesh out of the skin and discard the skin. Place the flesh in a small food processor with the remaining ingredients. Process until smooth. Adjust consistency with milk, as desired. Taste and adjust seasoning, as desired.
When the steak reaches 110ºF-115ºF, remove it from the cooker, place on a plate and cover loosely with foil. Immediately remove the door from your two door diffuser (or remove the entire heat diffuser) and place GrillGrates over the open fire. Set the temperature to 500ºF. When the cooker comes up to temp place the steak on the GrillGrates and grill on both sides until the internal temperature reaches 130ºF.
Remove the ribeye from the grill. Rest 5 minutes before slicing. Serve the steak on top of the sweet potato puree, topped with the crispy red onion straws and Century Sauce.