How to Make It
Preheat the oven to 350°. Butter a 9-inch round cake pan and dust with granulated sugar, pouring off the excess.
In a medium bowl, combine the goat cheese with the granulated sugar, lemon juice, lemon zest and vanilla and beat at medium speed until smooth. Beat in the egg yolks, 2 at a time, incorporating them completely before adding the next batch. Beat in the flour at low speed.
In another bowl, using clean beaters, beat the egg whites until firm but not dry. Beat one-third of the whites into the goat cheese mixture, then gently fold in the remaining whites. Spoon the batter into the prepared pan and bake for about 40 minutes, or until a skewer inserted in the center of the cake comes out clean. Transfer to a wire rack to cool completely.
To make a fruit sauce for the cake, lightly crush the raspberries and blueberries with 1 tablespoon of sugar and set aside for 10 minutes. Garnish the cake with additional whole berries.