Angel Food Cake with Three-Berry Compote

Preheat the oven to 350 °. In the bowl of a standing electric mixer, beat the egg whites at medium-high speed until frothy. Add the cream of tartar and beat until firm peaks form. Add the granulated sugar, 2 tablespoons at a time, beating for 10 seconds before adding more. Beat in the vanilla. Once all of the sugar has been added, beat the whites at high speed until stiff, about 4 minutes. In a medium bowl, whisk the cake flour with the confectioners' sugar and salt. Sift the dry ingredients over the beaten whites in 3 batches, folding gently with a large spatula until incorporated. Spoon the batter into an ungreased 10-inch angel food cake pan (do not use nonstick). Bake for 40 minutes, until the cake is risen and golden. Invert the cake in the pan onto a bottle neck and let cool. In a large saucepan, combine the berries, sugar and lemon juice and simmer until the juices are released, about 10 minutes. Let cool slightly. Using a knife, loosen the cake from the pan and remove the side of the pan. Loosen the cake from the pan bottom and the tube. Transfer the cake to a plate. Slice the cake and serve with the warm compote.