In a bowl, combine the origanum, chilli powder, all-spice, cumin, coriander and paprika together to make a spice rub.
Lightly coat the chuck roast in olive oil, season well with salt and black pepper and then rub the spice mix all over the meat.
Heat a splash of olive oil in a large pot over a high heat and lightly brown all sides of the roast to seal the meat and lock in the juices. Remove from the pot and set aside.
Lower the heat (add more olive oil if necessary), add the onions and gently fry until lightly caramelised. Stir in the garlic and jalapeño andcook for a further minute.
Pour the tomatoes, beef stock, orange juice and lime juice into the pot, stir to combine and bring to the boil.
Halve or quarter the chuck if it is too large and submerge the beef into the braising liquid. Cover with a tight-fitting lid and simmer on a low heat for 2 hours. Then remove the lid and cook for a further 30 minutes to allow the sauce to thicken.
In the meantime, make the fresh salsa by chopping the red onion, tomatoes, coriander and optional chilli as instructed above and mix together in a bowl. Squeeze the lime juice over the top, stir to combine and season to taste with salt and pepper. Refrigerate until needed.
Place the chuck roast on a chopping board and leave to cool slightly. Using two forks or your hands, pull the beef apart to create a shredded texture and return the pulled chuck to the braising liquid to coat in the sauce and warm through.
Heat up the tortillas directly on your stovetop, either using a gas burner on a low flame or an electric plate on a low heat (use a little non-stick spray for an electric plate). Warm each tortilla for about 30 seconds to 1 minute, flipping and repeating on the second side. Once heated and slightly charred wrap the tortillas in a clean dishcloth to keep warm. Repeat until you have warmed all of your tortillas.
Generously fill each tortilla with smoky, melt in your mouth pulled beef, shredded cabbage and fresh pico de gallo. Spoon over some saucy tomato salsa and a squeeze of lime juice.