Preparation: Preheat your oven to 350 degrees F. Prep your cake pans. This is a 3 layer cake - so you'll need 3 - 9" cake pans. You can grease and flour your pans, or you can use a non-stick spray specifically for baking.
Prepare the strawberry mixture by combining buttermilk, fresh strawberries, and freeze-dried strawberries in a blender.
Blend until smooth. Set aside.
For this recipe you need egg whites. So separate your eggs and discard the yolks. Allow the whites to sit at room temp for about 30 minutes. Set aside.
In a medium sized bowl - combine flour, baking powder, baking soda and salt. Stir to combine. Adding salt when baking activates the baking soda. So don't skip the salt! Set aside.
Whip butter using the paddle attachment of your stand mixer for 30 seconds.
Add sugar and beat until combined.
Stir in vanilla.
Add room temperature egg whites. Beat for 3 minutes. You'll have a pale, light batter.
Add ⅓ of the blended strawberry mixture. Add ⅓ of the flour mixture. Beat just until combined. Repeat until you have used the remaining flour and strawberry mixture.
Divide the batter between your 3 prepared cake pans. Give them a little shake to even the batter. Bake at 350 for 30 minutes, or until a toothpick comes out clean.
Let cakes cool in pans for 10 minutes, and then turn over onto a cooling rack and let cook completely.