Preheat your oven to 350°F (175°C) and prepare an 8x8-inch baking pan by greasing it with butter and lining it with parchment paper.

In a food processor, finely grind 1 cup of pistachios with the zest of one lemon. In a mixing bowl, combine this with 1 cup of cake flour, 1 teaspoon of baking powder, and 1/2 teaspoon of baking soda.

In another bowl, whisk together 1 cup of sour cream, 1/2 cup of milk, and 1 teaspoon of vanilla extract until smooth.

In a stand mixer, beat 1/2 cup of softened butter with 1 cup of sugar and a pinch of salt until light and fluffy.

Add 3 large eggs to the creamed mixture one at a time, mixing well after each addition.

Gradually add the dry ingredients to the wet mixture, alternating with the sour cream mix until combined.

Pour the batter into the prepared pan and smooth the top. Bake for 35-40 minutes, or until a toothpick comes out clean.

Cool the cake in the pan for about 10 minutes before transferring it to a wire rack to cool completely.

Prepare the frosting by mixing 8 ounces of mascarpone cheese with 1 cup of confectioners’ sugar and a splash of vanilla extract until smooth.

Spread the mascarpone frosting evenly over the cooled cake and sprinkle chopped pistachios on top.