3. Preheat the oven to 350°F (175°C). Lightly coat two 9-inch (23cm) springform pans with canola oil spray, then line the bottoms with parchment paper.
4. To make your flax egg, whisk together the flaxseed and soy milk in the bowl of a stand mixer until a smooth paste forms. If there are any lumps, push a small rubber spatula against the side of the bowl to break them up. Let sit for 10 minutes to bloom and thicken.
5. Whisk in the canola oil, coconut sugar, flax egg, brewed espresso, vanilla, and apple cider vinegar.
6. In a large bowl, whisk together the all-purpose flour, spelt flour, cinnamon, espresso powder, baking powder, baking soda, and salt.
7. Add the dry ingredients to the wet ingredients. Using the paddle, beat on medium speed until a smooth batter forms, 1 to 2 minutes. Stop the mixer halfway through and use a rubber spatula to scrape down the sides and bottom of the bowl to ensure there are no lumps or dry patches.
8. Divide the batter evenly between the prepared pans, about 700g per pan. Bake until a skewer inserted in the centre of the cakes comes out clean, 25 to 30 minutes. Let the cakes cool in their pans on a cooling rack for 15 to 20 minutes. Remove the ring from the pan and let the cake layers cool completely before frosting, about 60 minutes.