Zebra/Marble Cake

I always like to make this cake (not because I like to eat, but because of the look!). Anyway, here's the recipe:

Ingredients:
1. 125g butter
2. 150g caster sugar
3. 1 tsp vanilla essence
4. 3 eggs
5. 20g milk powder
6. 100ml water
7. 225g self-raising flour
8. 1.5 tbsp cocoa powder

Steps:
1. Preheat oven to 180⁰C. Dissolve milk powder in water.
2. Cream softened butter with sugar until pale and creamy. Beat in vanilla essence.
3. Beat in eggs one at a time, beating well after each addition.
4. Fold in about half the sifted flour and then half the milk. Continue until both flour and milk finish.
5. Bake for 45 minutes.

and this is what I've got~nice color huh?