Preheat the oven at 180ºC and grease the pan with cooking oil
Add the sugar into a bowl, melt the butter at the microwave, add it to the sugar and stir.
Add the eggs to the batter and stir well.
Sieve the flour and the cocoa powder and add it to the batter and stir until it seems ok (like a cake batter).
Put the batter in the pan and add it 40 minutes to the oven at 180ºC.
Later, unmold it, put into a plate and eat!