1. Preheat the oven to 350°F (175°C). Grease two 8-inch round cake pans and line the bottoms with parchment paper.

2. Whisk together the flour, baking powder, baking soda, salt, and finely ground pistachios in a medium bowl.

3. In a large bowl, beat the softened butter and granulated sugar until light and fluffy.

4. Beat in the eggs one at a time, then add the vanilla extract and lemon zest.

5. Add the dry ingredients alternately with the milk and sour cream, mixing just until combined. Do not overmix.

6. Divide the batter evenly between the prepared cake pans and smooth the tops.

7. Bake for 25 to 30 minutes, or until a toothpick inserted in the center comes out clean.

8. Let the cakes cool in their pans for about 10 minutes, then transfer them to a cooling rack and cool completely.

9. For the mascarpone cream, beat the chilled mascarpone, powdered sugar, and vanilla until smooth.

10. Gradually add the cold heavy cream and whip until thick and spreadable. Do not overbeat.

11. Place one cake layer on a serving plate and spread a generous layer of mascarpone cream over the top.

12. Place the second cake layer on top and cover with additional mascarpone cream or frost the entire cake.

13. Decorate with chopped pistachios, fresh berries, and a light dusting of powdered sugar.

14. Chill the assembled cake until ready to serve, then let it sit at room temperature for about 15 to 20 minutes before slicing.