Preheat oven to 350 degrees Fahrenheit and grease three 8-inch round cake pans.

In a medium bowl, whisk together cake flour, baking powder, baking soda, and salt.

In a large bowl, cream together 0.75 cup butter and granulated sugar until light and fluffy, approximately 5 minutes.

Gradually add egg whites and vanilla extract, beating well after each addition.

Combine buttermilk and berry puree in a separate container.

Alternately add the dry ingredients and the buttermilk mixture to the creamed butter, beginning and ending with the dry ingredients.

Divide batter evenly among the prepared pans and bake for 30 to 35 minutes or until a toothpick comes out clean.

Cool cakes in pans for 10 minutes, then transfer to wire racks to cool completely.

For the frosting, beat cream cheese and 0.5 cup butter until smooth, then gradually add powdered sugar and 1 teaspoon vanilla until light and airy.

Place one cake layer on a serving plate, spread with frosting, and top with a layer of sliced fresh berries.

Repeat with the second layer, then top with the final cake layer and frost the top and sides of the entire cake.

Garnish with remaining fresh berries before serving.