Preheat your oven to 350°F (175°C). Grease and flour your cake pan.
In a large mixing bowl, combine the flour, sugar, cocoa powder, baking powder, baking soda, and salt.
Add the eggs, milk, oil, and vanilla extract to the dry ingredients. Mix until smooth.
Gradually add the boiling water to the batter, mixing continuously. The batter will be thin.
Pour the batter into the prepared cake pan.
Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.