Method

• Preheat oven to 180 °C/350 °F
• Brush six 6” round cake pans with melted butter and line bottom of each cake pan with parchment paper.
• In a large bowl, sift together flour, baking powder and salt; set aside.
• In the bowl of an electric mixer fitted with the paddle attachment, cream together butter and sugar until pale and creamy.
• Slowly add in eggs one at a time and vanilla extract until well combined.
• Slowly stir in one third of the flour mixture and then half of the milk. Repeat with half of remaining flour and all of the milk, finally ending with remaining flour. Mix until just combined.
• Divide batter evenly between six medium bowls (~240g each).
• Stir in enough of each food colour to each bowl, until desired colour is achieved.
• Transfer each bowl of coloured batter to an individual cake pan.
• Bake in a preheated oven at 180 °C/350 °F and for about 12 minutes, or until a skewer inserted in the middle comes out clean.
• Remove cakes from oven and let them cool down completely.
• To make Italian meringue buttercream, place 160g of sugar and 40ml of water in a saucepan and bring to a boil until sugar reaches 116°C/ 240°F.
• Meanwhile, whisk egg whites and remaining 80g of sugar in an electric mixer until soft peaks.
• When sugar has reached the desired temperature, slowly add cooked sugar syrup in a slow and steady stream into the egg whites while the mixer is on high speed.
• When all the sugar has been added, keep whipping the meringue to cool to room temperature.
• Once meringue is at room temperature, add in butter a bit at a time into the meringue while whisking at medium speed. When all the butter is added, whisk until buttercream is smooth.
• Assemble cake with violet layer at the bottom. Spread enough buttercream before layering with the blue layer. Continue until the red layer is on top. Cover entire cake with buttercream.