Preparation

1. Combine ground flax with water and set aside.
2. Place a rack in middle of oven; preheat to 325°. Lightly butter an 8½x4½” or 9×5″ loaf pan. Line with parchment paper, leaving overhang on both long sides.
3. Bring cider to a boil in a medium saucepan over medium-high heat. Reduce heat and simmer until cider is reduced to ¾ cup, 8–10 minutes. Set aside ¼ cup reduced cider to use on the outside of the bread.
4. Transfer remaining reduced cider to bowl and let cool 5 minutes. Stir in vegan sour cream and vanilla and set aside.
5. Melt 8 Tbsps. (save one for later) vegan butter in same saucepan (no need to clean) over low heat. Let cool slightly.
6. In a bowl whisk your dry ingredients, (flour, cornstarch, baking powder, baking soda, 1 tsp. salt, ½ tsp. cinnamon, and ¼ tsp. nutmeg in a medium bowl to combine.)
7. Whisk the flax eggs and ¾ cup sugar in a large bowl, 2 minutes, gradually add melted vegan butter in a steady stream; continue to whisk until fully combined and emulsified (no spots of fat should remain). Reserve saucepan.
8. Whisk dry ingredients into flax egg mixture in 3 additions, alternating with reserved vegan sour cream mixture in 2 additions; whisk just until no lumps remain. Batter will be thin. Don’t over mix.
9. Scrape into pan and set on a rimmed baking sheet. Bake cake, rotating halfway through, until deep golden brown and a tester inserted into the center comes out clean, 65-80 minutes. Transfer pan to a wire rack and poke top of cake all over with a toothpick. Spoon 3 Tbsp. reserved reduced cider over; let cool 10 minutes.
10. Meanwhile, mix a big pinch of salt, remaining ¼ cup sugar, ½ tsp. cinnamon, and ¼ tsp. nutmeg in a small bowl. Melt remaining 1 Tbsp. butter in reserved saucepan and mix into remaining 1 Tbsp. reduced cider.
11. Using parchment paper, lift cake onto rack and set rack inside rimmed baking sheet. Peel away parchment from sides. Brush warm butter mixture over top and sides of cake. Sprinkle generously with sugar mixture to coat every surface (use parchment to help rotate cake and collect any excess sugar). Remove parchment and let cool completely before slicing.