In a medium glass bowl, combine 2 cups granulated sugar and zest from 1 large orange by using your hands to rub the zest and sugar together. Once the zest is fully incorporated into the sugar, cover with plastic wrap and allow the zest to infuse orange oil into the sugar, preferably overnight (see baker's notes). Once you're ready to use the sugar, uncover the sugar and use a fork to break up the sugar clumps.
Preheat the oven to 350 (F). Prepare three 6-inch round cake pans (or two 8-inch round cake pans) by spraying generously with cooking spray and lining the bottom of each pan with parchment paper circles. Spray the top of each parchment circle and set aside.
In the bowl of a freestanding electric mixer fitted with a paddle attachment, combine 1 3/4 cups all-purpose flour, 2 cups orange-infused granulated sugar (from step 1), 3/4 cup unsweetened cocoa powder, 2 teaspoons baking soda, 1 teaspoon baking powder, and 1 teaspoon salt. Mix on low speed until throughly combined. In a separate medium bowl, combine 1 cup buttermilk, 1/2 cup oil, 2 eggs, and 1 orange liqueur. Whisk together gently until just combined.
With the mixer on its lowest speed, slowly add the wet ingredients (from the 3rd step) to the dry ingredients (from the 2nd step). Add 1 cup hot coffee. Continue stirring on low speed until just combined, before stopping the mixer and using a rubber spatula to scrape the bottom and sides of the bowl and mix into the batter. The batter will seem really liquidy, but again, this is normal. Pour the batter into the prepared pans and bake in the preheated oven for 35 to 40 minutes, until a skewer inserted into the center of each cake comes out with a few crumbs and the tops of each cake bounce with a sponge-like texture when poked gently with your finger. When the cakes are ready, remove from the oven and let the cakes cool in the pans on a wire rack for 30 minutes, before turning out to cool. Remove parchment paper and allow the cakes to cool completely before frosting.