Preheat your oven to 170ºC (340ºF) and line the bottoms of three 20cm (8-inch) baking pans with parchment paper.

Pulse the unsalted pistachios in a blender until flour-like. Sift with all-purpose flour, baking powder, baking soda, and salt.

Cream butter and sugar in a large bowl for 3 minutes. Add eggs two at a time, mixing well. Gradually incorporate half of the dry ingredients, then sour cream, oil, vanilla, and remaining dry ingredients.

Divide batter among the pans, smooth tops, and bake for 20-23 minutes or until a toothpick comes out clean. Cool in pans for 10 minutes before transferring to wire racks.

In a medium saucepan, combine frozen raspberries, sugar, lemon juice, and cornstarch mixed with water. Stir occasionally and cook for 10-15 minutes until thickened.

Remove from heat and let cool in the fridge for at least 1 hour to set.

Beat room-temperature butter until smooth. Gradually add powdered sugar and raspberry powder in two stages, mixing well.

Incorporate whole milk and vanilla extract, whipping until fluffy.

Layer one cooled cake on a serving plate, spread buttercream, then raspberry jam. Repeat with the second layer and top with the final cake.

Chill assembled cake for 20 minutes. Apply a crumb coat, then frost top and sides with remaining buttercream.

Decorate with additional raspberry or pistachio toppings if desired.