Melt the chocolate in a double boiler, stirring occasionally with a rubber spatula. (Alternatively, use a heatproof bowl set over a pot of simmering water, making sure the bottom of the bowl is not touching the water.) Flip a sheet pan upside-down, spray it with nonstick baking spray, and line it with parchment paper. Using an offset spatula, spread the melted chocolate in an even layer over the parchment paper. Place in the freezer to set, 30 minutes.
In a small bowl, combine water and flax meal. Set aside to thicken, 30 minutes and up to overnight.
Preheat oven to 350 F. Combine dry ingredients in a mixing bowl: both flours, baking powder, baking soda, salt, and cinnamon. Set aside.
Put the bananas and vanilla extract in a plastic deli container, then purée with an immersion blender, 30 seconds. Add the puréed banana to a large mixing bowl along with canola oil, apple cider (or orange juice), the flax mixture, and the sugar. Stir to combine. Add the dry ingredients and stir just to combine, until there's no visible flour. Stir in the chopped pecans.
Pull chocolate from the freezer and break it up into shards. Using a rubber spatula, fold the shards into the batter. The folding motion will further break up the chocolate, which is okay.
Spray a standard loaf pan with nonstick baking spray. Scrape batter into the pan and smooth out the top. Tap the pan on a hard surface to settle the batter. In a small bowl, mix the sugar and cinnamon and sprinkle on top of the batter. Bake 1 hour.
Banana bread is done when a cake tester comes out clean. Let cool completely in the pan, then run a knife around the edge, invert onto a plate, slice, and serve.