This is, by far, the best Chocolate Sponge Cake! It's light and airy, moist and tender, rich and chocolatey. It's truly every chocolate lover's dream come true!
Preheat the oven to 350°F (180°C) and grease a 9-inch (23cm) cake pan with cooking spray. In a medium bowl, whisk together flour, cocoa powder, baking powder, and salt.
In a separate bowl, beat eggs and sugar with an electric mixer until the mixture becomes thick and pale. Add oil, vanilla extract, and milk to the egg mixture and beat until well combined.
Gradually add the dry ingredients to the wet mixture while beating on low speed. Pour the batter into the prepared cake pan and smooth the surface with a spatula.
Bake for 25-30 minutes, or until a toothpick inserted into the center of the cake comes out clean. Remove the cake from the oven and let it cool for 10 minutes before removing it from the pan.