« » Make the lemon cake: Preheat oven to 350 degrees with rack in center. Butter a 10-inch round cake or springform pan, dust with flour, and tap out any excess.
In a large bowl, sift flour and baking powder; set aside.
Place sugar and lemon zest in the bowl of an electric mixer; rub the ingredients together between your fingers until the sugar is moist, grainy, and has absorbed as much of the zest as possible. Return bowl to mixer.
Using the whisk attachment, beat in eggs on medium high until the mixture is pale and thick, about 3 minutes.
With the mixer on lowest speed, beat in milk. Add reserved flour mixture; beat until incorporated. Add lemon juice, melted butter, and olive oil; beat until blended.
Pour about one third of the batter into the prepared pan; there should be just enough batter to form a thin, even layer. Arrange the raspberries on top of the batter. Pour the remaining batter over the raspberries, and use a rubber spatula to gently spread batter so that it runs down between the berries and just covers them (you'll have a very thin top layer of batter).
Bake cake until it's golden and pulling away from the sides of the pan, and a cake tester inserted into the center comes out clean, 30 to 33 minutes.
Remove the cake from the oven, and immediately unmold it onto a wire rack. Invert cake so it is right side up, and allow to cool to room temperature. Once cooled, the cake is ready to serve or to decorate with meringue.
Make the meringue and assemble the dessert: Preheat oven to 475 degrees with rack in the center. Place the cooled cake on a parchment-lined baking sheet, and set aside.
In the clean, dry bowl of an electric mixer fitted with the whisk attachment, beat egg white until it holds soft peaks. Add granulated sugar in a slow, steady stream; continue beating until firm, glossy peaks form.
Using a metal icing spatula or a spoon, immediately spread the meringue over the top of the reserved cake. Dust the meringue with confectioners' sugar.
Bake the cake until lightly browned, 4 to 6 minutes. Garnish the cake with the mixed berries, if desired, and serve.