Preheat your oven to 350°F (175°C) and prepare two cake pans by greasing them and lining the bottoms with parchment paper.
Cream the butter and sugar: In a large bowl, beat together softened butter and sugar until fluffy (3-5 minutes).
Add eggs and vanilla: Add eggs one at a time, mixing fully after each addition, and stir in vanilla extract.
Combine dry ingredients: In a separate bowl, whisk together the flour, ground pistachios, baking powder, baking soda, and salt.
Add dry ingredients alternately with buttermilk: Gradually fold the dry ingredients into the butter mixture, alternating with the buttermilk. Mix until smooth.
Bake the cake layers: Divide the batter evenly between the pans and bake for 30-35 minutes, or until a toothpick comes out clean. Let cool in the pans for 10 minutes, then transfer to a wire rack.
Make the frosting: Whip the heavy cream to soft peaks, then fold it into the mascarpone and powdered sugar mixture.
Assemble the cake: Once the cakes are completely cool, spread a layer of raspberry preserves on the first cake layer, followed by a layer of frosting. Place the second cake layer on top, frost the entire cake, and decorate with fresh raspberries and pistachios.
Chill and serve: Chill the cake for at least 1 hour before slicing. Serve and enjoy!