Preheat the oven to 325 degrees F. Spray organic oil or spread butter onto 3 4-inch diameter cake pans. Line each cake pan with a circular piece of parchment paper.
Place the all-purpose flour, cake flour, baking soda, baking powder, and kosher salt into a medium sized bowl. Whisk and set aside.
Add unsalted butter, brown sugar, and granulated sugar to an electric mixer. Mix these ingredients on medium-high speed until fluffy (approx. 2 minutes). Then, add the egg and continue to mix until the egg is well incorporated.
Place the Greek yogurt, milk, raspberry extract, and vanilla extract into a measuring cup. Set aside.
Next, add half of the flour mixture and half of the liquid mixture to the electric mixer. Once fully mixed. Turn off the mixer. Add in the remaining flour mixture and liquid mixture. Mix on a medium-low speed until the batter is well mixed.
Evenly distribute the cake batter to the 3 4-inch cake pans. Bake for 25 minutes or until inserted toothpick comes out clean.
Allow the cakes to fully cool before frosting.
Lemon Frosting:
Place the unsalted butter into an electric mixer. Beat on medium speed until light and fluffy. Slowly add in the powdered sugar in small increments at a time. If the buttercream becomes too thick, add a tablespoon of lemon juice. Scrape sides of the bowl often.Once all the powdered sugar is added. Add the vanilla extract. Mix until fully incorporated.**
Notes
**If adding the thinly sliced strawberries to your cake. I recommend adding them in a single row in-between the cake layers after spreading the lemon frosting on the cake layer.