Preheat oven to 350°F (175°C) and grease a round cake pan.
In a bowl, whisk together flour, cocoa powder, baking powder, and sugar until well combined.
In another bowl, mix eggs, melted butter, milk, orange juice, and zest until smooth.
Gently combine the wet and dry ingredients without overmixing.
Pour the batter into the prepared pan and bake for 25-30 minutes or until a toothpick comes out clean.
Allow to cool completely before glazing with a mixture of powdered sugar, cocoa powder, and orange juice.
