For the bison dry rub: Blend the chiles, cumin seeds and corn powder in a spice grinder into a smooth powder and set aside. Transfer to a mixing bowl and add the sage, garlic powder, smoked paprika, salt and pepper. Mix thoroughly and keep in a mason jar.
For the braised bison: Preheat a grill for cooking over medium-high heat and preheat the oven to 225 degrees F.
Place the bison on a cookie sheet and cover it with oil. Cover with about 5 tablespoons dry rub, thoroughly covering the entire cut. Sear the meat all over on the grill, about 5 minutes per side, then transfer to a Dutch oven and add enough stock to cover the meat halfway. Cover with foil, then the lid and bake until tender, about 12 hours.
Remove the meat from the hot stock to a cookie sheet and let rest, at least 20 minutes.
For the chile reduction: Deseed chiles and toast them. Char onion and tomatoes. Put chiles, onion, tomatoes and garlic in a blender along with 2 cups bison stock left behind from cooking the bison and blend until smooth. Add salt and pepper to taste.
Use tongs to pull the meat apart and use your hands to separate the fat (discard the fat).
Cut meat into smaller pieces and return to the Dutch oven with the hot stock and 1 cup chile reduction.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.