Rainbow Birthday Layer Cake

1. Cream together softened butter, sugar, and vanilla sugar

2. Gradually add eggs, mixing well after each addition

3. Whisk together flour, baking powder, salt, and lemon zest in a separate bowl

4. Alternately add the flour mixture and milk to the butter mixture

5. Divide the batter evenly among 6 bowls

6. Add red food coloring to one bowl, yellow to another, green to another, and blue to another

7. For the fifth bowl, mix 1 drop red and 3-4 drops yellow to create orange

8. For the sixth bowl, mix 1 drop blue and 3-4 drops red to create purple

9. Mix each bowl until the color is uniform

10. Grease a 20 cm springform pan

11. Preheat the oven to 180°C (convection: 160°C)

12. Pour one colored batter into the prepared pan and spread evenly

13. Bake in the preheated oven for 15-20 minutes

14. Let the cake cool, then remove from the pan

15. Repeat with the remaining batters, one color at a time

16. Drain the cream cheese well

17. Beat the cream cheese with softened butter and powdered sugar until smooth

18. Place the first cake layer (purple) on a serving plate

19. Spread about 2-3 tablespoons of cream on the layer

20. Place the next layer (blue) on top

21. Repeat with the remaining layers

22. Frost the entire cake with the remaining cream

23. Decorate the cake with colorful sugar sprinkles as desired

24. Refrigerate until ready to serve

Tips

1. To help the thin cake release easily, line the bottom of the pan with a round piece of parchment paper, which can be easily peeled off after baking