Preheat oven to 350°F/175°C. Coat 3 8-inch round cake pans with vegetable cooking spray. Cut parchment paper into two 8-inch circles. Place the round parchment paper in the bottom of the pans. Spray papers with vegetable cooking spray. Set aside.
Mix together the sugar, flour, cocoa powder, baking soda, baking powder, and salt. Zest the orange and add the orange zest to the cocoa flour mixture. Mix until combined.
Juice the zested orange. You should have roughly ¼ cup of orange juice. Supplement with lemon juice if it's not quite ¼ cup.
In a separate bowl combine orange juice, cold water, vegetable oil, applesauce, vanilla, and instant coffee. Stir to combine. Pour this in with the cocoa/flour mixture and stir until just combined.
Measure the water into a pyrex (heat resistant) measuring cup. Heat in the microwave until hot (not boiling). Pour the hot water into the batter and stir to combine.
Pour half the batter into each of the prepared pans.
Bake for 25 to30 minutes until the edges have pulled away from the sides of the pan and the center of the cake is set. A tester inserted in the center should come out clean.
If using a 9x13 cake pan, bake for approximately 40 to 45 minutes.
Remove cakes from the oven and allow them to cool for 10 minutes. Then invert the cakes onto wire racks and cool completely before frosting.
While the cakes are cooling, make the vegan chocolate frosting. Spread half of the frosting over one of the cooled cakes. Add the second cake on top and top it with more frosting, reserving some frosting for the sides. Garnish with orange wedges.
Store leftover cake in the fridge.