NOTE: It is SUPER IMPORTANT that all the room temperature ingredients listed above are room temperature and not cold or hot.
If your ingredients just came out of the refrigerator or the strawberry reduction is too hot, your mixture could curdle during the process of making the cake batter and become ruined.
Adjust an oven rack to the middle position and preheat to 350ºF/176ºC.
Grease three 6″ cake pans or two 8″ cake pans with cake goop or preferred pan release
Add butter to stand mixer and beat at medium speed until smooth and shiny, about 30 seconds. Gradually sprinkle in the sugar, beat until mixture is fluffy and almost white, about 3-5 minutes. Add the egg whites approximately two at a time, beating 30 seconds between.
Whisk the flour, baking powder, baking soda, salt, and lemon zest in a medium bowl.
Combine the strawberry reduction, milk, vanilla extract, lemon extract, strawberry extract and food coloring in a separate medium bowl.
With the mixer at the lowest speed, add about a third of the dry ingredients to the batter, followed immediately by about a third of the milk mixture, mix until ingredients are almost incorporated into the batter. Repeat the process 2 more times. When the batter appears blended, stop the mixer and scrape the sides of the bowl with a rubber spatula.
Divide the batter evenly between the prepared pans. Smooth the tops with a rubber spatula. Bake cakes until they feel firm in the center and a toothpick comes out clean or with just a few crumbs on it, about 30-35 minutes.
Transfer pans to a wire rack and let cool for 10 minutes. Invert cakes onto the rack and pop cakes out of pans. Cool completely before frosting.
Place egg whites and powdered sugar in a stand mixer bowl. Attach the whisk and combine ingredients on low and then whip on high for 5 minutes
Add in your butter in chunks and whip with the whisk attachment to combine. It will look curdled at first. This is normal. It will also look pretty yellow. Keep whipping.
Let whip on high for 8-10 minutes until it’s very white, light and shiny.
Add in strawberry reduction and salt and continue whipping until incorporated.
Switch to a paddle attachment and mix on low for 15-20 minutes to make the buttercream very smooth and remove air bubbles. This isn’t required but if you want really creamy frosting, you don’t want to skip it.
Decorating the cake
Place your first layer of strawberry cake onto a cake plate or cake board. Trim off the dome if needed with a sharp knife so the top of the cake is flat.
Add a very thin layer or your cooled reduction over the cut surface. This helps soak into the cake and adds moisture and strawberry flavor.
Add a layer of strawberry buttercream, I shoot for about 1/4″. Smooth it with your offset spatula until it’s flat.
Frost the outside of your cake with the leftover buttercream and decorate with some fresh. strawberries if desired.
Make sure all your ingredients are room temperature or a little warm even. (eggs, milk, butter, puree) so that your ingredients mix together well.
When making your puree, the goal is to get as much liquid out as possible without burning the strawberries. The mixture should look like thick tomato sauce and reduced by half by the time you’re done.
You will use some of the reduction for the cake batter, some for the frosting and the rest for filling between the cake layers for extra moisture. Leftover puree can be stored in the fridge for up to one week or frozen for 6 months.
Make sure your frosting is very light and white before adding in the puree. Give it a taste, if it still tastes like butter, keep whipping it until it tastes like sweet ice cream.
If your buttercream looks curdled, it’s too cold. Take out 1/2 cup of buttercream and melt it in the microwave until its just barely melted. About 10-15 seconds. Pour it back into your whisking buttercream and it will become creamy.