Make the reduced strawberry puree first, and let cool: In a blender or food processor, puree the fresh strawberries. Transfer the puree to a small saucepan over medium-low heat and simmer until reduced to ½ cup, about 25–35 minutes. Cool completely before using.

Preheat the oven to 350°F (177°C). Grease two 9-inch round cake pans, line with parchment paper, and grease the parchment paper.

Make the cake: Whisk the cake flour, baking powder, baking soda, and salt together in a medium bowl and set aside.

In a large bowl, beat the butter and sugar together until light and creamy. Add the egg whites and beat until combined, then add sour cream and vanilla and mix until combined. Slowly pour in the milk and add the dry ingredients. Mix until just combined, then fold in the reduced strawberry puree.

Pour the batter evenly into the prepared cake pans and bake for 24–25 minutes, or until a toothpick comes out clean. Cool in the pans for 1 hour before transferring to a cooling rack.

Make the frosting: Process freeze-dried strawberries into a fine powder. Beat together cream cheese and butter until smooth, then add confectioners' sugar, strawberry powder, milk, and vanilla. Beat until creamy, refrigerate for 1 hour before using.

Level the cakes using a serrated knife to create a flat surface. Place one layer on the cake stand, spread frosting on top, add the second layer upside down, and spread a crumb coat with a thin layer of frosting. Refrigerate until set.

Cover with remaining frosting and refrigerate the cake for at least 20 minutes before slicing.