Last year was rainbow, this year the 7 year old wanted a marble birthday cake. She prefers plain vanilla, so vanilla it is, just zhuje it up with colour and edible glitter decoration.

Makes 3-layer cake
4 c flour
4 tsp baking powder
1 tsp salt
300g butter, softened
1 3/4 c sugar
1 tbsp vanilla extract
4 eggs
red, blue and yellow food colouring

4 c icing sugar
300g butter, softened
2 tsp vanilla extract
4-6 tbsp hot water

Preheat oven to 170C. Line 3 20cm round sponge tins with baking paper.
In a small bowl whisk flour, baking powder and salt.
In a large bowl cream the butter and sugar until fluffy. Beat in vanilla, Add eggs one at a time and beat until combined. Fold in flour mixture.
Divide mixture evenly into 3 bowls. Colour each bowl pink, blue and yellow. Divide each bowl into thirds and put spoonfuls of each third into each cake tin, dotted around randomly. Repeat with the other two colours. Take a skewer or knife and swirl around the batter to form a marble pattern and smooth down evenly. I usually have thinner edges so I make a slight indentation in the middle of each cake to spread the batter to the edges.
Bake for 20-25 min until cooked through. Cool in the tins for 10 min then turn out onto a wire rack to cool completely.
Mix buttercream ingredients until smooth. Place a couple of dots of icing on the bottom of your serving plate or board and position the bottom cake layer on top. Spread with buttercream, place middle layer on top and spread with buttercream. Place the top layer on top and lightly ice all over the cake. This thin layer crumb coat prevents any stray crumbs from mixing into your final layer of icing. Place cake in fridge for 15-20 min to set the crumb coating.
Spread your cake with a final layer of buttercream and decorate as you wish!