Preheat the oven to 350°F (175°C).

Grease and flour two 9-inch round cake pans.

In a large mixing bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt.

In another bowl, whisk together the eggs, milk, oil, and vanilla extract.

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

Carefully stir in the boiling water, orange juice, and zest until smooth.

Pour the batter evenly into the prepared pans.

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

Allow the cakes to cool in the pans for 10 minutes before transferring to a cooling rack.