With the rack in the middle position, preheat the oven to 150 °C (300 °F).
In a blender, purée all the ingredients until smooth. Set aside.
Rub the meat with the chili powder. Season with salt and pepper.
In a large ovenproof pan, brown the meat in the oil. Add the barbecue sauce. Cover and bake for about 3 hours or until the meat is fork-tender. Remove the meat from pan and let cool on a plate. With a fork, shred the meat.
Bring the sauce back to boil and reduce for 8 to 10 minutes or until syrupy. Add the shredded meat and stir to combine. Adjust the seasoning. Serve with slices of cornbread.