Preheat oven to 180 degree

Beat butter and sugar together until smooth.

Crack in eggs and add vanilla, then beat again until well combined.

Add the zest of 1/2 orange and squeeze the juice of one orange and mix in. Sieve juice before mixing

Sieve in flour, bicarb and then gently fold into the mixture.

When well mixed, put roughly half of the mixture into a separate bowl.

To one bowl, add the cocoa and juice and mix in.

For more creamy and chocolaty texture I added one small, melted dairy milk chocolate.

Put half of your pale mixture into the tin. Then all of your chocolate mixture. Finally, add your remaining pale mixture.

For the marble look, zig-zag your knife through the mix.

Put in the preheated oven for 30 minutes but keep checking

Now combine the juice of remaining half orange with enough icing sugar to make a syrup consistency and a little zest too.

Once a golden crust is formed on the top and cake is cooked through the middle, remove from the oven and prick the top with a fork then pour over the prepared juice solution
It should be poured when cake is warm so that it is all absorbed.

Cut slices when cake is cooled down and enjoy