Indulge in this berried version of the traditional angel food cake.
1In steamer basket set over a saucepan of simmering water, steam blueberries and raspberries, covered, for about 10 minutes or until very soft and plump. Transfer to a plate lined with paper towels and let cool.
2In steamer basket set over a saucepan of simmering water, steam blueberries and raspberries, covered, for about 10 minutes or until very soft and plump. Transfer to a plate lined with paper towels and let cool.
3In a bowl, using a dry fine-mesh sieve, sift together flour, ¾ cup of the sugar and the salt. Sift into another bowl and then back into the original bowl (sifting a total of 3 times).
4 In a large metal or glass bowl, using an electric mixer, beat egg whites until foamy. Beat in cream of tartar until egg whites thicken. Gradually beat in the remaining sugar in a thin, steady stream. Continue to beat just until stiff, glossy peaks form.
5Sift one-third of the flour mixture over egg whites. Using a rubber spatula, gently fold in just until blended. Repeat with the remaining flour mixture in 2 more additions. Fold in vanilla.
6Pour about one-quarter of the batter into the pan. Sprinkle with half of the berries, smoothing top. Sprinkle with the remaining berries, then pour the remaining batter over the top. Gently run a narrow spatula or a knife through the batter to remove any large air pockets. Smooth top.
7Bake in preheated oven for about 40 minutes or until top is golden and springs back when lightly toughed. Immediately invert pan onto a wire rack, perching on the rim of the pan or placing the tube over an inverted funnel to lift cake in the air, if necessary. Let cool completely,. gently run a knife around the edge of the cake and press bottom through to remove ring. Invert cake onto a serving platter and carefully remove the bottom and tube section, letting cake drop onto the platter.