Preheat oven to 350 degrees. Prepare 3 8 inch cake pans, using butter and flour. Line the bottom of each pan with a circle of parchment paper.
In the bowl of a stand mixer, cream softened butter and sugar for about 3 minutes until mixture is light and fluffy. While mixture is creaming, in a medium bowl, whisk together flour, baking powder and salt. Set aside
Add mayonnaise (or sour cream) and vanilla extract to butter and sugar mixture. Mix until combined. Add egg whites two at a time, beating well after each addition. Scrape down the sides of the bowl.
Mix in half of the flour mixture and mix well. Then add in the milk and mix until well combined. Finally, add the other half of the flour mixture and mix until well incorporated.
Divide batter into prepared pans. Batter makes about 6 cups, so each pan should have about 2 cups of batter.
Bake for 21-23 minutes. A tester or toothpick placed in the middle of the cake should come out clean. Cool cake layers in their pans for about 6-10 minutes. Then remove the cakes and let them cool on a rack. Once layers are cooled to room temperature, chill them in the refrigerator for at least 30 minutes.
While cakes are chilling, prepare frosting. Mix room temperature butter and beat until creamy. Slowly add in powdered sugar. Combine until smooth. Add vanilla extracts, almond extracts and salt. Beat frosting until light and fluffy.
To assemble cakes: Place one layer on a serving plate or cake stand. Top with buttercream. Spread jam on the middle layer and invert it, placing the jam side on top of the bottom layer. Spread the top of the middle layer with buttercream. Repeat the same process with the jam on the top layer. Turn that layer upside down and place it on top of the middle layer. At this point, place the cake in the refrigerator for 30 minutes. After chilling, remove cake from refrigerator. Frost the top and outside of the cake. Decorate the top with fresh berries.