Coolest Princess Castle Rainbow Cake

My daughter requested a castle cake for her 5th birthday. She was very specific in her desire – it had to have pink walls, a purple roof, and be rainbow cake inside. Nothing like setting mummy a challenge!

All the details

After determining the size of the cake by the dolls I was using, and what tins I had available for use, I made all the building details ahead of time. I drew everything beforehand, making sure my sketches were proportional to the cake, and also designing my decorations and colour theme for every element.  For my very first time using fondant, I made individual purple roof tiles and marbled grey/black/brown to make pebbles for the path. I used blue food colouring to colour sugar for the moat. I very slowly and carefully coloured white chocolate purple (using Americolor gell paste Royal Purple) and piped windows and doors on baking paper to set.

The rainbow cakes

I made many small and normal sized (20cm) round cakes for use on the 2 main castle stories. To make the rainbow cakes, I mixed Betty Crocker vanilla cake as per packet instructions, then divided the mix into small bowls which were coloured with Americolor gell paste. I then spooned in to an oiled and lined tin, building up the colours, and baked as normal. I chose to cut circles out of round cakes to layer and make the larger towers. I used small jam sponge rolls for the smaller towers.

Castle Cake


I layered the cakes together with icing, and used thin dowel rods covered in alfoil to secure down through the towers and main cakes. I trimmed the tower cakes in to a point I was happy with. After a crumb coat, I covered the whole cake with white chocolate buttercream icing coloured with Americolor gel paste. I then placed the roof tiles on, the windows and the doors. Following my design sketches, I piped on vines and used premade sugar flowers as their blooms. I made my daughters initial \”A\” out of silver cashous. I iced the grass on, pouring the blue sugar as a moat. I iced the path grey and then placed the pebbles on top. Final touches on the day meant covering the roof tiles and path with opalescent edible shimmer and adding the dolls.

Is it the cake she dreamed of?

Upon revealing the cake to my daughter she was gobsmacked. She squealed and jumped up and down. It was exactly what she hoped for, and she was stoked to see Snow White and Rapunzel dolls on it, as she wished for them for her birthday.

The party guests were all “oohing” and “aahhhing”, saying how I could never top making a cake like this. Keeping the rainbow part a secret, my daughter got a real thrill from cutting the cake and revealing the rainbow inside. Wow! was the general reaction! It tasted wonderful too. It was a lot of cake, but that meant we had leftovers for my daughter to enjoy the next day. I was incredibly proud of this cake. I have never done any cake decorating courses. I just follow my instincts.

I personally don’t like children’s cakes being completely covered in fondant, so it’s always a goal for me to use soft icing, ready to make sticky fingers and icky faces. I think the memories of devouring birthday cakes as a child, should be full of sticky, gooey deliciousness. After all, kids enjoy getting messy!

Castle Cake