Preheat & Prep. To start, preheat oven temperature to 350 degrees F. Lightly grease an 8-inch round cake pan and line the bottom of the pan with parchment paper.
Combine Dry Ingredients. In a medium bowl, combine gluten-free flour, cocoa powder, cinnamon, salt, baking powder, and baking soda. Whisk to combine, then set flour mixture aside.
Rub Zest Into Sugar. In a large bowl, combine 1 Tablespoon orange zest with the granulated sugar. Use clean fingertips to rub the zest into the sugar until it's a light orange color and it smells citrusy and fragrant.
Combine Wet Ingredients. To the orange sugar mixture, add warm almond milk, 1/3 cup melted coconut oil, vinegar, and vanilla. Whisk to combine.
Add Dry Ingredients To Wet Ingredients and stir until just evenly combined, with no big lumps or dry patches remaining.
Bake. Pour cake batter into prepared pan and gently tap on the counter to remove any extra air bubbles. Bake cake in preheated oven 35-40 minutes, or until a toothpick inserted in the center of the cake comes out clean with just a few moist crumbs.
Cool & Turn Out. Let the cake cool 5 minutes in the pan. Run a thin knife around the edges of the cake, then turn the cake out onto a wire rack to finish cooling completely. I place the top side of the cooling rack face down on top of the cake, then flip it over so the cake is on top of the cooling rack. Let the cake cool completely before adding ganache.
Make Ganache & Decorate The Cake. In a microwave-safe bowl, heat coconut milk, 1/2 Tablespoon coconut oil, and orange zest to steaming in the microwave. (It should be near a simmer or boil.) Add chocolate chips and stir to combine until the chocolate chips are melted and the ganache is smooth and glossy. Pour over the top of the cake and smooth the ganache with an offset spatula. Let the ganache set. (I like to add garnish right before serving.)
Serve & Store. Enjoy cooled cake with your favorite garnish. Store leftover cake in an airtight container 1-2 days at room temperature, or freeze up to 2 months.