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Arrange oven rack to the lower third of the oven. Preheat the oven to 350°F (180°C). Sift the cake flour, confectioners' sugar and salt together 4 times. Set aside.
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Wipe the bowl and whisk attachment of an electric mixer with paper towel and lemon juice, to remove any trace of grease. Add the egg whites and beat on the lowest speed until they start to become frothy, about 30 seconds. Stop the mixer and sprinkle the cream of tartar over the egg whites. Beat on medium speed until the egg whites thicken just slightly and you can see swirl lines in the mixture from the whisk (very soft peaks), about 1 minute. Add the superfine sugar 1 tablespoon at a time and beat until the egg whites thicken and reach soft/medium, droopy (not stiff) peaks, 1-2 minutes. Beat in the vanilla and almond extract.
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Remove the bowl from the mixer. Sift the dry ingredients 1/4 at a time on top of the meringue and fold gently but thoroughly with a rubber spatula.
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Divide the batter evenly into 3 bowls and add a few drops of each colour to create each tinted batter layer by folding every so gently until blended: few drops Soft Pink to one bowl; Regal Purple to another; turquoise to the third.
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Gently transfer the batter, one layer at a time, to an ungreased 10" angel food cake pan and smoothing each with a small offset spatula or back of a spoon. Bake on the lower rack of the oven until the top of the cake springs back when touched lightly, and when a skewer inserted into the cake comes out clean, about 35 minutes. Don't check the cake before 35 minutes, or you could deflate your cake, but also try not to over-bake.
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Remove the cake from the oven and invert the whole pan onto a wire rack so it cools upside down. Let cool for one hour and then loosen sides around the center and outside of the cake using a thin metal spatula or knife. Gently coax the cake out of the pan onto the wire rack and let cool completely. Take your time with this step--you can even use your fingers to loosed the bottom edges, by reaching down between the cake and the pan, pushing the cake away from the sides. It will bounce right back. Do this all around the bottom before pulling the cake out of the pan.