Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.

In a mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt.

In another bowl, mix the melted butter and sugar until combined. Add the eggs, buttermilk, vanilla extract, and blood orange zest, and mix well.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Pour the batter into the prepared cake pan and smooth the top.

Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.

Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

In a small bowl, whisk together the powdered sugar and blood orange juice until smooth.

Once the cake is completely cool, drizzle the glaze over the top of the cake.