Using an electric mixer, beat the butter on medium speed for a minute or two. Add the sugar and cream the butter and sugar together for about 2 to 5 minutes until it is fluffy and light in color. Scrape down the bowl with a rubber spatula one or two times as needed. Beat in the eggs, the egg whites and the vanilla extract until everything is blended.
Combine all the ingredients by alternately adding the dry ingredients and the wet ingredients to the bowl with the butter and sugar. Pour the batter evenly into the two prepared pans.
Note: If making the day ahead, do not top with the berries until a few hours before serving. The cake layers can be made and frozen up to a week ahead of time. Wrap and store leftovers in the refrigerator for about 5 days.