Preheat oven to 350°F (177°C). Grease three 8-inch round cake pans, line with parchment paper rounds, then grease the parchment paper.

Pulse the pistachios in a food processor until ground into very fine crumbs. Pour 1 and 1/2 cups of pistachio crumbs into a large bowl and reserve the remaining crumbs for garnish. Whisk in the cake flour, baking powder, baking soda, and salt. Set aside.

Beat the butter and granulated sugar together in a bowl using a mixer until smooth and creamy, about 3 minutes. Scrape down the sides and bottom of the bowl. Beat in the egg whites until combined, about 2 minutes. Then beat in the sour cream, vanilla extract, and almond extract. Scrape the bowl as needed.

Add the dry ingredients to the batter, then start the mixer on low speed. Slowly pour in the milk and mix until combined. You may need to whisk by hand to ensure no lumps remain.

Divide the batter evenly among the prepared cake pans. Bake for 21–23 minutes or until a toothpick inserted into the center comes out clean. Allow cakes to cool completely in the pans on a wire rack.

In a large bowl, beat the cream cheese and unsalted butter together until smooth, about 2 minutes. Add the confectioners’ sugar, vanilla extract, and a pinch of salt. Beat on low speed for 30 seconds, then on high speed for 3 minutes until creamy.

Layer off the tops of the cakes to create a flat surface. Place 1 cake layer on a cake turntable or serving plate. Evenly cover the top with frosting. Add the second layer followed by more frosting, then top with the third layer. Spread remaining frosting all over the top and sides and garnish with remaining pistachios.

Refrigerate the cake for at least 30 minutes before slicing.