Zebra Cake (Failed)

This is the zebra cake i make yesterday, still failed. The bottom like the previous zebra cake even i change the water to hot water. I get this recipe from Jo's Deli Bakery.

Here the ingredients and method.

6 eggs
110g castor sugar
150g cake flour
1/2 tsp baking powder
1/2 tsp emulsifier
100g butter (melted)
30g condensed milk
1 tsp vanilla essence (optional)

2 tsp cocoa powder
3-4 tbsp water
1 tsp choc emulco
Dissolve cocoa powder and choc emulco in water

1. Preheat oven at 170 degC. Prepare and grease a 8 inch round cake pan.
2. Sift flour and baking powder. Set aside.
3. Beat eggs, flour in (2), castor sugar and emulsifier on high speed for 10 minutes or until batter turns light and creamy, i.e. thick ribbon state. To test, lift beater. Batter drops from beater should disappear when you count from 1 to 10.
4. Pour melted butter, condensed milk and vanilla essence (if any). Mix at slow speed.
   Divide batter into 2 equal portions. Fold chocolate solution into one of the batters.
5. Using tablespoon, scoop 3 tbsp of uncoloured batter into centre of cake pan. Then, scoop 3 tbsp of chocolate batter onto the uncoloured batter you just scooped into the pan.
6. Repeat until you have finished about half of the batter. Reduce to 2 scoops each now and continue layering as (6). Reduce the amount of batter gradually until you only pour 1 scoop of each batter finally. The circles become smaller and smaller as your pour.
7. Sprinkle almond nibs or flakes to cake. Bake at 170 degC for 35 minutes.
8. Let cake in pan for 10 minutes before turning it on to a wire rack to cool complete