The ultimate summer dessert! Make the cake the day before so it’s quick and easy the next day to finish with whipped cream and berries.
Place the oven rack in the lower third of the oven and heat the oven to 350 degrees. Butter a 9-inch round cake pan.
In a clean, dry bowl, beat the egg whites until soft peaks form. Set aside.
In a medium bowl combine the flour, baking soda, and baking powder and set aside.
In the bowl of an electric mixer with a paddle attachment, cream together 3/4 cup butter and sugar for 2 minutes. Beat in the egg yolks, one at a time, and then add the vanilla and blend well. Add the dry ingredients and the buttermilk alternately in two to three increments, scraping the bowl once or twice during the blending process.
Remove the bowl from the mixer and gently fold in the egg whites. Pour the batter into the prepared pan and bake for about 45 minutes, until lightly golden brown. Test for doneness by inserting a thin wooden skewer into the center of the cake. If the skewer comes out clean, the cake is done.
Cool the cake for 10 to 15 minutes before removing it from the cake pan.
In a medium bowl, combine the strawberries, 1 pint blueberries, 1 pint raspberries, orange juice, and sugar. Let sit for 1 hour at room temperature.
Meanwhile, in a medium bowl beat the cream and sugar together with an electric mixer until stiff peaks form.
Using a serrated knife, slice the cake horizontally into 3 even layers. Place the bottom cake layer on a serving plate. Spoon or brush some of the liquid from the strawberry mixture onto the cake and let it soak in. Spoon half the berries evenly on top of this layer and spread about a third of the whipped cream over the berries.Top with the second layer of cake, repeat the process with the juice, spoon the rest of the berries over this layer, and top the berries with another third of the whipped cream. Add the top layer of cake and spread the remaining whipped cream on the top. Place the reserved whole berries on top of the cake. Refrigerate until ready to serve, up to 3 hours.