Preheat the oven to 350°F (175°C). Grease and line two 8-inch round cake pans or three 6-inch pans, tapping out excess flour. Sift the flour, baking powder, baking soda, and salt together.

In a stand mixer, beat 1/2 cup softened unsalted butter with 1 cup granulated sugar until light and fluffy, about 3–4 minutes.

Add the 3 large room-temperature egg whites one at a time, mixing until incorporated. Stir in 3 teaspoons Rodelle vanilla bean paste.

Whisk together the sour cream and milk. With the mixer on low, add one-third of the dry ingredients and half the milk mixture. Repeat, ending with dry ingredients.

Divide the batter evenly between the pans. Bake for 22–28 minutes until a toothpick comes out clean. Cool in pans for 10 minutes before transferring to wire racks.

Beat cream cheese and butter until silky. Gradually add powdered sugar until you reach the desired firmness. Fold in pureed fresh strawberries.

Level cake layers if needed. Stack layers with frosting in between and apply a crumb coat. Chill for 15–20 minutes before applying a final layer of frosting.

Decorate with fresh sliced strawberries if desired.