Preheat the oven to 180℃/375℉. Line an 8" circular cake pan (I use a springform pan) - See Notes to use two pans.
In a large bowl, or the bowl of a stand mixer, combine the flour, baking powder, baking soda, cocoa powder, sugar and a pinch of salt.
Make a well in the dry mix, and add the eggs, hot water, milk and oil. Fold together to form a smooth (if a little runny) batter.
Pour the batter into the lined tin and bake 30-35 minutes, until a skewer inserted comes out clean. Let cool on a wire rack.