Preheat your oven to 350 degrees
In a small bowl, combine the softened butter and 2 tbsp cocoa powder. Mix well to form a thick paste
Brush the inside of a 9-inch Bundt pan with this paste, coating well. Set aside
In a bowl of a stand mixer or a large bowl with a whisk, combine flour, remaining ½ cup of cocoa, granulated sugar, baking soda, salt, and cinnamon
Add in the orange juice, orange zest, mayonnaise, balsamic vinegar, and vanilla and mix well until no lumps remain
Pour batter into prepared pan and bake in preheated oven for 45-minutes, or until a toothpick inserted in the middle comes out clean. Mine took exactly 45-minutes, but oven temperatures vary so watch yours closely
While the cake bakes, prepare the glaze by mixing the sugar, cocoa, and orange juice until well combined. Set aside
Carefully remove the cake from the oven and allow it to sit for 10-minutes
Once 10-minutes has passed, lay a piece of parchment paper over the top of the cake and place a cooling rack on top
Carefully flip the cake onto the cooling rack and slowly lift the pan off
Allow the cake to cool completely before drizzling the glaze overtop