Lemon Pistachio Cake

1. Preheat the oven to 325F. Grease and line the base of two 6×2 inch round cake pans with circular parchment paper cutouts.
2. In a large mixing bowl, whisk together the flour, pistachio flour, baking powder, and salt.
3. In the bowl of a stand mixer or a separate large mixing bowl, add the sugar and lemon zest. Use clean hands or a fork to massage/incorporate the zest into the sugar. This helps to release the natural oils from the lemon zest, resulting in a more aromatic, flavorful bake.
4. Add the butter into the bowl with the lemon-infused sugar. Using a stand mixer fitted with a paddle attachment or a hand mixer, cream the mixture together at medium-high speed for 2-3 minutes until thick and fluffy in appearance.
5. Mix in the sour cream and vanilla extract into the creamed butter mixture. Next, beat the eggs into the wet batter one at a time stopping to scrape the sides and base of the mixing bowl with a rubber spatula after each addition.
6. With the mix set at low speed, mix half of the dry ingredients into the wet batter followed by all of the lemon juice, and ending with the remaining dry ingredients.
7. Stop the mixer and scrape the sides and base of the mixing bowl with a rubber spatula. Resume mixing the batter at medium speed for 1 minute to ensure that you have a smooth cake batter.
8. Equally, divide the cake batter between the prepared baking pans and bake for 28-30 minutes or until a toothpick inserted into the center of the cakes comes out clean with a few moist crumbs.
9. Cool the cakes in the baking pans for 10-12 minutes before transferring them to a cooling rack to cool to room temperature.

Lemon Pistachio Buttercream 

1. In the bowl of a stand mixer fitted with paddle attachment or with a hand mixer and large mixing bowl, cream the butter and lemon zest together at medium-high speed until thick and fluffy in appearance, about 3-4 minutes.
2. Reduce the mixer speed to low and slowly mix in the confectioners’ sugar followed by the pistachio flour until fully incorporated into the creamed butter, about 1-2 minutes.
3. Increase the mixer speed back to medium and mix 1 tablespoon lemon juice into the buttercream. If it is too thick, mix in additional lemon juice 1 teaspoon at a time until you have a thick but spreadable consistency. I ended up using 4 teaspoons of lemon juice.
4. If buttercream consistency is too soft, mix additional confectioners’ sugar into the buttercream 1/4 cup at a time until you have a thick but spreadable consistency.

Assembly

1. Level the cooled cake layers with a serrated knife or cake leveler, if needed, for a flat, stackable surface.
2. Place the first cake layer faced up on a serving plate or cake stand. Spoon 1/2 cup of the frosting on top of the cake and smooth it out into an even layer using an offset spatula.
3. Place the second cake layer on top of the buttercream layer face down and coat the entire cake in a thin layer of buttercream for a crumb coat.  Refrigerate the cake to set the crumb coat for 30-60 minutes.
4. Apply a thick layer of the remaining buttercream over the entire surface of the cake. Use a bench scraper and offset spatula to smooth out the buttercream.
5. For vertical ridge buttercream design, I used this tutorial.
6. Make a border on top of the cake with the chopped pistachios before serving.