Wash, clean, and hull the strawberries. Place them in a food processor and pulse until smooth. Pass it thru a sieve to remove seeds.
Pour into a saucepan over medium heat. Cook until the strawberry puree has reduced to almost ⅓ of its original volume.Pro tip - Reducing the puree will concentrate the flavor with less liquid.
Preheat the oven to 325°F / 165°C / Gas Mark 3.
Grease and line 2× 6-inch baking pans with parchment paper. You can also double this recipe to make 2 x 8-inch round cakes.Pro tip - I am baking in 2 pans, so I can torte in half to make four. But, you can also use 3 x 6-inch round pans to make 3 layers. That way you don't have to torte.
Dry ingredients - Combine the flour, baking powder, baking soda, and salt – set aside.
In the bowl of a stand mixer with the paddle attachment, cream the butter, oil, and sugar until light and fluffy. Add the eggs, one at a time, making sure each is well incorporated. Pro tip - Adding eggs one at a time will prevent the batter from curdling.
Next, add the flour, sour cream, and strawberry puree in three batches making sure to scrape the sides of the bowl. Then, add the vanilla and strawberry extract and combine well.Pro tip - Do not overmix at this stage as we do not want to activate the gluten in our flour.
Pour the batter into the two prepared baking pans and bake for 20 to 25 minutes on the middle rack or until a center inserted in the center comes out clean. Pro tip - It is a great idea to use cake strips around my baking pans to prevent a dome. That way you don't lose much height on your layer cakes.
Once baked, leave in the pan for no more than 10 minutes. Then, invert onto a cooling rack to cool completely. Pro tip - Always frost cakes only when they are completely cooled. Otherwise, the frosting will melt.
Place egg whites and sugar in the bowl of the stand mixer.Pro tip - Make sure the bowl is grease-free. Otherwise, the egg whites will not whip.
Using a whisk, place the bowl over a double boiler and constantly whip until all the sugar has dissolved and the egg whites are fairly warm (about 160 F).Pro tip - You don't need a thermometer, as long as all the sugar has completely melted your eggs are ready to use.
Take the bowl off the heat and whip the egg whites until you have a thick meringue with stiff peaks.Pro tip - It is best to start whipping eggs at medium speed then increase speed as you go for the best meringue.
Let the mixer continue to whip on medium-low until the mixer bowl feels cool to touch. Then, gradually add butter, one cube at a time, with the mixer at medium speed.Pro tip - It is VERY important that the meringue is cooled completely before you add the butter. Otherwise, you will have a soupy mess.
Once all the butter is added, whip on medium-high for 2 minutes. Lastly, add the vanilla and strawberry extract. Combine well until everything is well combined.
Watch this video showing how I level, torte, and fill the cakes.Pro tip - Make sure the cakes are completely cold. Otherwise, the frosting will melt. Plus, the cakes are more delicate to handle. Chilling the cakes makes them easier to work with.
Using a bread knife or cake leveler, cut the domes off the cake layers. Then, divide each layer in half horizontally so you have four layers (2 x 2 = 4 layers).
Brush each layer with the cooled simple syrup. Pro tip - To enhance the strawberry flavor you can add a few drops of strawberry extract or strawberry puree to simple syrup to make a strawberry syrup.
Place the cake in the fridge to chill for 10 to 15 minutes.Pro tip - Chilling the cake at this point will ensure the layers don't move when you frost the outside. Though, if you leave the cake uncovered in the fridge for too long it can dry out. So, 10 minutes is all you need.
Divide the remaining buttercream in two. Add pink gel food color to one half. Put both colors of buttercream in a piping bag with a star piping tip nozzle.
Pipe swirls around and top of the cake. These swirls are exactly what you would do on a cupcake just smaller in size. Decorate as desired.
Use room temperature ingredients especially butter and eggs as these can cause the batter to curdle.
Add eggs one at a time making sure each is well emulsified before you add the next. This will give a light and airy cake.
The cake layers will stay fresh for up to four days at cool room temperature, longer if kept in the fridge.
The cake layer without frosting can be frozen for up to a month or more.
The cake once frosted is best kept in the fridge.
The Swiss meringue buttercream (SMBC) has egg whites which are considered perishable.
In good weather, a cake frosted with SMBC can be kept at room temperature for up to 2 days.
The nutrition information and metric conversion are calculated automatically. I cannot guarantee its accuracy. If this data is important to you please verify with your trusted nutrition calculator. Thank you