Grease cake tins with butter and dust the base and sides throughly with flour

Preheat oven to gas mark 3/ 170°C/ 325°F

Take your butter and eggs out of the fridge and put them on the worktop to come to room temperature

In your 1st bowl add your freeze dried raspberries (10g), 2 tablespoons of milk and a pea size amount of the red food gel and stir well to combine. Add more food gel for a more vibrant colour

In your 2nd bowl add orange zest and juice, 2 tablespoons milk and a pea size amount of orange food gel and stir well to combine

In 3rd bowl add lemon zest and juice, 2 tablespoons milk and a pea size amount of yellow food gel and stir well to combine

Shell 70g pistachios then add them to a food processor and grind to a powder or grind in a pestal and mortar. Add your ground pistachios to your 4th bowl along with 2 tablespoons milk and a pea size amount of green food gel and stir well to combine

Put 70g of frozen blueberries into blender and blitz until pureed. Put your pureed blueberries in your 5th bowl along with 2 tablespoons of milk and a pea size amount of blue food gel and stir well to combine

In your 6th bowl add 1 table spoon of lavender sugar, 2 tablespoons milk and a pea size amount of purple food gel and stir well to combine

Beat 750g of unsalted butter and 750g of caster sugar with a paddle attachment on a medium-high speed for 6-7 minutes until light and fluffy.  Remember to stop and scrap down the sides of the bowl every minute to make sure all the butter and sugar is fully incorporated

Crack 10 eggs into a medium-/large bowl and give them a a quick whisk

Turn your mixer back on to a medium speed and add your eggs in 6-7 stages mixing well between each stage

Add 750g of self raising flour and a pinch of salt to batter and mix on a low speed until combined, remebmer to scrap down the sides of your bowl a few times to get all the flour fully incorporated

Put a large clean bowl on to your scales and place all your batter into the bowl

Divide the amount of batter you have by 6

Now one at a time place each of your coloured bowls on your scales make sure not to forget to zero your scales each time when you place a new bowl on your scales

Place your divided amount of batter in each bowl

Mix each bowl of batter just until you see the batter is coloured evenly

Place your batter into your prepared tins and bake for 20 minutes. If you don't have 6 cake tins you're going to have to wait until the ones in the ovens have cooked and cooled before continuing cooking the other colours

Cakes are ready when you insert a skewer, tooth pick or knife into the centre of the cake and it comes out clean

Leave cakes to cool in their tins for around 15 minutes then place on a cooling rack to cool completely

Once cooled put each of your cakes on a piece of baking paper to make moving the cakes around easier

Level off the tops of each of your cakes with a cake leveler or bread knife

Place your cake drum in the center on top of one of your leveled cake and cut around the drum with your pointed knife. Be very careful when doing this because you can scrape off the silver coating of you cake drum which will ruin the appearance of your final presentation. If you have a loose bottom cake tin the same size as your cake drum cm inches then use that instead to protect your cake drum or have 2 cake drums just incase. Do this for all your cakes

You can skip the next steps and fill and stack your cake all on one day but if you want to work ahead of time wrap each layer with 2 lots of cling film tightly and then 1 layer of foil and place in the freezer for up to a week. If stacking on the same day freeze for at least 3 hours

Add 450gbutter to mixer and beat with your paddle attachment or hand held mixer on a high speed for 5 minutes until pale and fluffy

Add 1kg icing sugar in 2 batches and beat for 3 minutes between each one

Turn mixer on to a low speed add 1 tsp vanilla and 6-7 tbsp. water then turn the speed up to a high speed and beat for 2 minutes until light and fluffy

Cover with cling film until your ready to use it

Set out all your equipment, turntable, cakedrum, spatula, palette knifes, scraper/benchscraper and then get all your layers out of the freezer keeping the foil and clingfilm on

Place your cake board/drum in the center of your turntable and place a tablespoon of buttercream on the center of your board so your first layer sticks to the board and doesn't slip or move

Unwrap your purple layer and place it onto your cake board push down slightly on the cake to make sure the buttercream is holding the cake and board securly

Measure out 1/3 cup of butter cream and spread it evenly over your purple layer

Unwrap your blue layer and place it on top of the butter cream, making sure to apply a little pressure to secure your cake to the buttercream

Measure out 1/3 cup of buttercream and sprerad it evenly over your blue layer

Unwrapped your green layer and place it on top of the buttercream add 1/3 cup butter of buttter evenly across your cake and reapeat with your yellow cake 1/3 buttercream, orange cake 1/3 buttercream and finaly add your red layer but don't add any buttercream on top of it just yet

With your offset spatula crumb coat the entire cake, sides and top with a thin layer of buttercream (there's a step by step video on )

Place your cake in the fridge for 1 hour to harden

Using your offset spatula cover the the side of your cake with most of the buttercream (save 1/3 for the top). Run the flat, straight edge of your spatula or bench scraper around the edges of the cake to smooth out the buttercream

Add the last of your buttercream to the top of the cake and with your offset spatula or bench scraper smooth the buttercream from the outside in for a smooth finish

Decorate with some rainbow gelatine bubbles