Combine the brown sugar, chili powder, cumin, thyme, salt and pepper in a bowl.
Rub mixture over all sides of the pork butt.
Wrap in foil or place in an air-tight container and place in refrigerator for 1-4 hours.
Preheat oven to 300 F.
Heat oil in a large Dutch oven over medium-high heat. Brown pork on all sides. Remove to a plate.
Add onions and sautee for 4 minutes.
Add garlic and sautee for another minute.
Add the tomato paste, vinegar and hot sauce. Stir and cook for 2 minutes.
Add the pineapple and its juices. Stir.
Add the pork and its juices back into the pot.
Bring to a boil, then cover. Transfer to the oven.
Cook for 3-4 hours. Every 30 minutes, spoon the juices over the top of the meat. After 2 hours, flip the meat over (carefully! do not splatter yourself).
Remove from oven. Remove the pork to a plate and let cool until you can handle it, 15 or so minutes. Pull pieces of the pork off and shred with your fingers or a fork. Discard any fatty pieces you encounter.
Place the Dutch oven back on a stovetop burner. Scrape off any accumulated fat.
Bring to a boil and let cook until the sauce thickens, about 15 minutes, stirring often.
Add the shredded pork back the pot. Remove from heat. Add in the coriander and stir.
Serve over buns or on tacos.