Mix all the dry ingredients, sift them, and put them in a mixing bowl.
Melt the butter in a saucepan.
Add eggs, melted butter, and water to the bowl with the dry ingredients.
Mix everything together with an electric mixer until the batter is well combined.
Pour the batter into a greased baking pan approximately 23x33 centimeters in diameter.
Bake the cake on the second lowest rack for about 35 minutes at 170 degrees Celsius (338 degrees Fahrenheit) without fan.
Check if the cake is done by inserting a wooden skewer into the center of the cake.
The cake should not be baked too long; it should be slightly sticky in the center.
Let the cake cool before applying the icing.
Put cocoa, powdered sugar, soft butter, cinnamon, and warm milk in a bowl.
Whisk everything together with the electric mixer until it forms a thick icing.
Spread the icing on the cake when it is cold.
Keep the display on
Notes
The cake tastes really good and is very quick to make. If you want to make a portion that fits the oven's baking tray, then use a double portion of batter.
The cake can be frozen, and it actually gets better from it.