Start by making the strawberry puree reduction. Combine one pound pureed strawberries, 1 tablespoon sugar and 2 teaspoons lemon juice in a small saucepan. Stirring occasionally, simmer over medium-low heat for 25 minutes or until the mixture has reduced by half. You should end up with a little more than 1/2 cup. Allow the reduction to cool completely before adding to the cake batter.: As the fruit simmers, you will notice the bubbling sound soften into a gentle simmer, and a fragrant, jam like aroma will rise from the saucepan. The mixture should reduce until it is slightly syrupy and a little more than 1/2 cup remains, which concentrates the sweet tartness of the fresh strawberries . Cooling the reduction completely before adding it to the batter prevents the eggs and butter from losing their structure. A common mistake is rushing the reduction on too high a heat, which can scorch the sugars and give a cooked flavor, so maintain medium low and stir occasionally to prevent sticking.
Preheat oven to 350°F. Spray two 9-inch round cake pans with cooking spray, then line the bottoms with parchment paper.: When the oven reaches the set temperature, it will have an even dry heat that helps the cake rise and set properly. Preparing the pans with cooking spray and parchment ensures smooth release; lining the bottoms prevents tearing when you invert the layers. Visual cues include the parchment sitting flat against the base and pans feeling warm but not hot when you handle them. Avoid placing pans in the oven before it has fully preheated, which can cause uneven rising and dense centers.
Add 2 3/4 cups flour, 2 1/2 teaspoons baking powder, 1 teaspoon salt, and 1/4 teaspoon baking soda to a medium mixing bowl. Whisk together and set aside.: Whisking the all purpose flour , baking powder , salt , and baking soda aerates and evenly distributes leavening. You want a uniform pale mixture without visible clumps, which prevents pockets of leavening or salt in the baked cake. Doing this step by hand is quick, and a common oversight is skipping the whisking, which can yield uneven texture or uneven rise.
In the bowl of a stand mixer fitted with a paddle attachment, beat 1 cup butter and 2 cups sugar on medium speed until light and fluffy. Add 4 egg whites, 1 1/2 teaspoons vanilla extract, 1/2 teaspoon strawberry extract, and 1 1/2 teaspoons lemon zest and continue to beat on medium speed until well combined and fluffy.: As you beat the unsalted butter and granulated sugar on medium speed, the mixture will lighten in color and feel fluffy to the touch, indicating air incorporation. Adding the egg whites , vanilla extract , optional strawberry extract , and lemon zest creates a fragrant, silky base. If the mixture looks curdled after adding egg whites, stop mixing and scrape the bowl, then continue; over mixing at high speed can deflate the emulsion and make the batter less tender.
Reduce the mixer speed to low and add in half of the dry ingredient mixture. Mix until combined. Slowly add in 1/2 cup milk and continue mixing until it is fully incorporated. Add in 1/2 cup of the cooled strawberry reduction and the remaining dry ingredients, mixing just until combined. Mix in a few drops of pink or red food coloring, if using, to achieve your desired color. Scrape down the sides and bottom of the bowl as needed to make sure the coloring is even throughout. Divide the batter evenly between the 2 pans.: Reducing speed and alternating dry mixture with whole milk encourages even incorporation without overworking the batter. When the batter looks evenly moistened with no streaks of dry flour, it is ready. After adding 1/2 cup of the cooled strawberry reduction, the batter will take on a pale pink tint and a bright fruity aroma. Scrape the bowl so there are no hidden streaks of flour, and avoid over mixing once the last dry ingredients are added, which can lead to a tougher crumb.
Bake for 30 minutes, or until a toothpick comes out clean when inserted into the center of the cake. Allow to cool completely in the pans before removing and assembling the cake. Once cooled, wrap the cake layers in plastic wrap and place into the freezer for at least 20 minutes before assembling.: A visually even distribution helps layers bake uniformly, which is important for stacking. Use a scale or measure by eye to get similar volumes. Smooth the tops gently so they bake evenly. If one pan has noticeably more batter, its center may remain underdone while the other is fully baked, so take a moment to level them before placing in the oven.
To make the frosting, place 1 1/2 cups freeze-dried strawberries into a food processor and pulse until it makes a fine powder. Set aside.: During baking you will see the cakes rise and the edges pull slightly from the pan, and a toothpick inserted into the center should come out clean. The top should be springy when pressed gently. Letting the cakes cool completely in the pans prevents the structure from collapsing from a sudden temperature change. A frequent error is removing hot cakes too soon and attempting to invert them; they may break apart. Be patient, and allow them to cool thoroughly.
In the bowl of a stand mixer fitted with a whisk attachment, beat 6 ounces cream cheese and 1/2 cup butter on medium speed until completely smooth and creamy. Reduce to a low speed and add in 3 cups powdered sugar, strawberry powder, 1 teaspoon vanilla, and 1 tablespoon of milk. Increase to medium speed and beat until creamy. Add another tablespoon of milk if the frosting needs to be thinned out. It should be a spreadable consistency.: Chilling wrapped layers firms the crumb, making them easier to trim and stack. After a short freeze, the layers are less likely to crumble when you assemble the cake or level domed tops with a serrated knife. This step makes decorating simpler and produces neater layers. Skipping the freeze can result in torn edges when frosting, so if you want tidy assembly, the chill is worth the wait.
Place the first cake layer on a cake stand or serving plate. Spread about 1 cup of frosting across the cake top. Top with the 2 nd cake layer and spread the remaining frosting across the cake and down the sides. Garnish with strawberries, if desired.: Processing the freeze dried strawberries into a fine powder releases concentrated aroma and color without adding moisture. The powder should resemble soft dust, and when pressed between fingers it should not feel gritty. This concentrated powder amplifies strawberry flavor in the frosting without thinning it. A coarse grind will leave grainy specks in the frosting, so aim for a fine texture.
Beat cream cheese and butter until smooth: Combining softened cream cheese and salted butter on medium speed yields a silky base for the frosting. Reducing speed before adding powdered sugar prevents a cloud of sugar dust. Once powdered sugar, strawberry powder, vanilla extract , and whole milk are added, increase speed to create a creamy, spreadable texture. If the frosting seems too stiff, add milk one teaspoon at a time; if it becomes too loose, chill briefly. Overbeating can incorporate too much air and cause a slightly soupy texture when it settles.
Assemble and frost the cake: Placing the first layer on a stand and spreading about 1 cup of frosting creates a stable base. The frosting should feel smooth and spread easily without tearing the crumb. After stacking the second layer, spread the remaining frosting across the top and down the sides for an even coat. Garnish with fresh strawberries if desired. A common pitfall is applying too much pressure when spreading, which can drag crumbs into the frosting, so use a thin crumb coat first if you want a pristine exterior.