To make the pork belly: Preheat the oven to 160°C. Score the pork skin lengthwise, every half inch. Brush with the canola oil, tamarind and honey. Place the apples cut-side down in a roasting pan and place the pork on top. Add the apple juice to the bottom of the pan and braise until the meat is fork-tender, about 3 hours.
To make the hoisin balsamic sauce: To a bowl, add the molasses, black bean paste, tamari, sesame oil, balsamic, chili paste and pepper and mix well. Set aside.
To make the dough: Into a large bowl, add the water and yeast and set aside for 1 minute. Whisk in 2 tablespoons of the canola oil. To a food processor add the sugar, baking powder and salt with the flour and pulse 2 to 3 times to combine. Pour the yeast mixture into the processor in a steady stream and continue mixing for about 20 seconds. If the dough doesn't come together, add warm water a tablespoon at a time and continue to mix for 50 to 60 seconds. Coat a ceramic bowl with 1 tablespoon of the canola oil. Place the dough in the bowl and cover with plastic wrap and a tea towel. Let rise until nearly doubled, about 1 hour.
Lightly dust a work surface with flour and roll the dough into a log. Cut the dough into 16 even parts. Roll each part into a ball, and then use your fingertips to flatten each ball into a 3-inch disc. Brush some canola oil on one half of each disc and fold over into a semicircle. Place the buns on parchment paper and place in a bamboo steamer over boiling water. Steam until the buns are puffed, 6 to 8 minutes.
To finish the buns: Remove the skin from the pork and roughly chop. Slice the pork belly against the grain. Brush the steamed buns with the apple juice-braising liquid. Add some pork belly, and dress with cucumbers, green onions and hoisin balsamic sauce.