At a glance
This colorful layer cake comes together with whipped egg whites folded into a light sponge batter, which you'll divide and tint with vibrant gel colors before baking—just go easy on the food coloring since it's super potent. The magic happens when you layer the rainbow batter into the pan and bake it briefly, then finish with a creamy mascarpone filling and white frosting that beautifully contrasts those cheerful layers. Plan for an overnight chill to let everything set perfectly.
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Egg yolk mixture and whisked whites
Separate the eggs into yolks and whites. Beat the yolks with the sugar, and whisk the whites into stiff peaks (adding a pinch of salt).
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Fold the yolks and whisked whites into the flour
Mix the flour with the baking powder and sift it through a fine sieve into a bowl. Add the sweetened yolks, then gently fold in the whisked egg whites.
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Six colourful bowls
Divide the batter between six smaller bowls and tint each one with the colour you want. A little food colouring really goes a long way — I actually overdid a few of the layers, which could have turned out much lighter.
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