Brush the cake tin with butter. Sprinkle some flour in it and tap so the flour will cover the tin. Take the acces flour out of the tin.
Mix the butter with the sugar on high speed in 3 minutes airy.
Add the eggs one by one, while mixing. Add the next egg when the former one is incorporated.
Mix in the vanilla extract and salt.
Put the mixer on low speed and mix the self rising flour through the batter. Stop mixing when the flour is incorporated.
Divide the batter into two separate bowls.
In a bowl add the cocoa and hot water until it becomes a paste.
Mix the cocoa paste into the second bowl with a spatula.
Take the tin and add two tablespoons of cocoa batter on the bottom. Then add two tablespoons vanilla batter, followed by two tablespoons of cocoa batter. Continue until all the batter is done.
Take a knife and swirl with the tip through the batter in the tin.
Put the tin in the oven and bake for 60 minutes. Check if the cake is done by pricking a wooden skewer into the middle of the cake. When it comes out dry the cake is done. If it is a bit wet, bake for another 5 minutes, check again and repeat until the cake is done.
Take from the oven, let it slightly cool for about 5 minutes and then loosen the cake from the tin on a wire rack. Let it cool down to room temperature.